Bacterial endotoxin: Chemical constitution, biological recognition, host response, and immunological detoxification

A Comparison between SARS-CoV-2 and Gram-Negative Bacteria-Induced Hyperinflammation and Sepsis

Sepsis is a life-threatening condition caused by the body's overwhelming response to an infection, such as pneumonia or urinary tract infection. It occurs when the immune system releases cytokines into the bloodstream, triggering widespread inflammation. If not treated, it can lead to organ failure and death. Unfortunately, sepsis has a high mortality rate, with studies reporting rates ranging from 20% to over 50%, depending on the severity and promptness of treatment. According to the World Health Organization (WHO), the annual death toll in the world is about 11 million. One of the main toxins responsible for inflammation induction are lipopolysaccharides (LPS, endotoxin) from Gram-negative bacteria, which rank among the most potent immunostimulants found in nature. Antibiotics are consistently prescribed as a part of anti-sepsis-therapy. However, antibiotic therapy (i) is increasingly ineffective due to resistance development and (ii) most antibiotics are unable to bind and neutralize LPS, a prerequisite to inhibit the interaction of endotoxin with its cellular receptor complex, namely Toll-like receptor 4 (TLR4)/MD-2, responsible for the intracellular cascade leading to pro-inflammatory cytokine secretion. The pandemic virus SARS-CoV-2 has infected hundreds of millions of humans worldwide since its emergence in 2019. The COVID-19 (Coronavirus disease-19) caused by this virus is associated with high lethality, particularly for elderly and immunocompromised people. As of August 2023, nearly 7 million deaths were reported worldwide due to this disease. According to some reported studies, upregulation of TLR4 and the subsequent inflammatory signaling detected in COVID-19 patients "mimics bacterial sepsis". Furthermore, the immune response to SARS-CoV-2 was described by others as "mirror image of sepsis". Similarly, the cytokine profile in sera from severe COVID-19 patients was very similar to those suffering from the acute respiratory distress syndrome (ARDS) and sepsis. Finally, the severe COVID-19 infection is frequently accompanied by bacterial co-infections, as well as by the presence of significant LPS concentrations. In the present review, we will analyze similarities and differences between COVID-19 and sepsis at the pathophysiological, epidemiological, and molecular levels.

Biomedyczne właściwości chitozanu – zastosowanie w inżynierii tkankowej Biomedical properties of chitosan: Application in tissue engineering

Inżynieria tkankowa to interdyscyplinarna dziedzina badań, która stosuje zasady inżynierii i nauk przyrodniczych do opracowywania substytutów biologicznych, przywracania, utrzymywania lub poprawy funkcji tkanek. Łączy medycy-nę kliniczną, inżynierię mechaniczną, materiałoznawstwo i biologię molekularną. Chitozan jest związkiem, który może być stosowany na szeroką skalę w biomedycynie, m.in. jako nośnik leków, nici chirurgiczne, materiały opatrunkowe przeznaczone do przyspieszonego gojenia ran oraz rusztowania komórkowe w inżynierii tkankowej. Chitozon spełnia najważniejsze kryteria dla biomateriałów, m.in. kompatybilność, odpowiednie właściwości mechaniczne, morfologia i porowatość, nietoksyczność i biodegradowalność. Rusztowania chitozanowe mogą sprzyjać adhezji, różnicowaniu i proliferacji na powierzchni komórek. Z chitozanu można tworzyć różne formy funkcjonalne w zależności od potrzeb i wymagań, w tym: hydrożele 3D, gąbki 3D, folie i membrany oraz nanowłókna. Ze względu na unikalne właściwości fizykochemiczne biopolimer ten może być również wykorzystany do oczyszczania białek terapeutycznych z endotoksyn bakteryjnych, co jest dziś istotnym problemem w oczyszczaniu produktu końcowego w zastosowaniach medycznych. Obecnie terapie oparte na białkach rekombinowanych znajdują szerokie zastosowanie w terapiach celowanych, inżynierii tkankowej oraz szeroko pojętej medycynie regeneracyjnej. Dlatego tak ważny jest współistniejący, dobrze zapro-jektowany system oczyszczania produktu białkowego, który nie zmieni swoich zasadniczych właściwości. Artykuł jest przeglądem aktualnych badań nad zastosowaniem materiałów bioaktywnych na bazie chitozanu w medycynie regene-racyjnej różnych tkanek i narządów (m.in. tkanki chrzęstnej i kostnej, tkanki skórnej czy tkanki nerwowej).

Adsorption-Based Detoxification of Endotoxins by Porous Flexible Organic Frameworks

Bacterial lipopolysaccharides (LPS, endotoxins) cause sepsis that is responsible for a huge amount of mortality globally. However, their neutralization or detoxification remains an unmet medical need. We envisaged that cationic organic frameworks with persistent hydrophobic porosity may adsorb and thus neutralize LPS through a combination of cooperative ion-pairing electrostatic attraction and hydrophobicity. We here report the preparation of two water-soluble flexible organic frameworks (FOF-1 and FOF-2) from tetratopic and ditopic precursors through quantitative formation of hydrazone bonds at room temperature. The two FOFs are revealed to possess hydrodynamic diameters, which range from 20 to 120 nm, depending on the concentrations. Dynamic light scattering and isothermal titration calorimetric and chromogenic limulus amebocyte lysate experiments indicate that both frameworks are able to adsorb and thus reduce the concentration of free LPS molecules in aqueous solution, whereas cytokine inhibition experiments with RAW264.7 support that this adsorption can significantly decrease the toxicity of LPS. In vivo experiments with mice (five males per group) show that the injection of FOF-1 at a dose of 0.6 mg/kg realizes the survival of all of the mice administrated with LPS of the d-galactosamine (d-Gal)-sensitized absolute lethal dose (LD₁₀₀, 0.05 mg/kg), whereas its maximum tolerated dose for mice is determined to be 10 mg/kg. These findings provide a new promising sequestration strategy for the development of porous agents for the neutralization of LPS.

Lipopolysaccharide-Induced Transcriptional Changes in LBP-Deficient Rat and Its Possible Implications for Liver Dysregulation during Sepsis

Sepsis is an organ dysfunction caused by the dysregulated inflammatory response to infection. Lipopolysaccharide-binding protein (LBP) binds to lipopolysaccharide (LPS) and modulates the inflammatory response. A rare systematic study has been reported to detect the effect of LBP gene during LPS-induced sepsis. Herein, we explored the RNA sequencing technology to profile the transcriptomic changes in liver tissue between LBP-deficient rats and WT rats at multiple time points after LPS administration. We proceeded RNA sequencing of liver tissue to search differentially expressed genes (DEGs) and enriched biological processes and pathways between WT and LBP-deficient groups at 0 h, 6 h, and 24 h. In total, 168, 284, and 307 DEGs were identified at 0 h, 6 h, and 24 h, respectively, including Lrp5, Cyp7a1, Nfkbiz, Sigmar1, Fabp7, and Hao1, which are related to the inflammatory or lipid-related process. Functional enrichment analysis revealed that inflammatory response to LPS mediated by Ifng, Cxcl10, Serpine1, and Lbp was enhanced at 6 h, while lipid-related metabolism associated with C5, Cyp4a1, and Eci1 was enriched at 24 h after LPS administration in the WT samples. The inflammatory process was not found when the LBP gene was knocked out; lipid-related metabolic process and peroxisome proliferator-activated receptor (PPAR) signaling pathway mediated by Dhrs7b and Tysnd1 were significantly activated in LBP-deficient samples. Our study suggested that the invading LPS may interplay with LBP to activate the nuclear factor kappa B (NF-κB) signaling pathway and trigger uncontrolled inflammatory response. However, when inhibiting the activity of NF-κB, lipid-related metabolism would make bacteria removal via the effect on the PPAR signaling pathway in the absence of LBP gene. We also compared the serum lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) levels using the biochemistry analyzer and analyzed the expression of high mobility group box 1 (HMGB1) and cleaved-caspase 3 with immunohistochemistry, which further validated our conclusion.

SERS Sensing of Bacterial Endotoxin on Gold Nanoparticles

Engineered gold nanoparticles (AuNPs) find application in several fields related to human activities (i.e., food and cosmetic industry or water purification) including medicine, where they are employed for diagnosis, drug delivery and cancer therapy. As for any material/reagent for human use, the safety of AuNPs needs accurate evaluation. AuNPs are prone to contamination by bacterial endotoxin (lipopolysaccharide, LPS), a potent elicitor of inflammatory responses in mammals. It is therefore important, when assessing AuNP immunosafety and immune-related effects, to discriminate between inflammatory effects intrinsic to the NPs from those caused by an undeliberate and undetected LPS contamination. Detection of LPS contamination in AuNP preparations poses different problems when using the current LPS detection assays, given the general interference of NPs, similar to other particulate agents, with the assay reagents and endpoints. This leads to time-consuming search for optimal assay conditions for every NP batch, with unpredictable results, and to the use in parallel of different assays, each with its weaknesses and unpredictability. Thus, the development of highly sensitive, quantitative and accurate assays able to detect of LPS on AuNPs is very important, in view of their medical applications. Surface-enhanced Raman spectroscopy (SERS) is a label-free, sensitive, chemical-specific, nondestructive and fast technique that can be used to directly obtain molecular fingerprint information and a quantitative analysis of LPS adsorbed on AuNPs. Within this study, we describe the use of SERS for the label-free identification and quantitative evaluation - down to few attograms - of the LPS adsorbed on the surface of 50 nm AuNPs. We thus propose SERS as an efficient tool to detect LPS on the AuNP surface, and as the basis for the development of a new sensitive and specific LPS-detection sensor based on the use of AuNPs and SERS.

Low endotoxin recovery and its impact on endotoxin detection

Endotoxin exists on the outer membrane of Gram-negative bacteria and poses risks to human health by triggering a series of immune responses. Therefore, its accurate detection is essential. The Limulus amoebocyte lysate (LAL) test is the most pharmacopeia-recognized and popular technique for endotoxin detection. Despite its wide industry adoption, the low endotoxin recovery (LER) phenomenon can compromise the LAL test's reliability. This review summarizes the possible reasons attributing to the LER phenomenon from three different perspectives: the endotoxin standards used in hold time study, protein active pharmaceutical ingredients, and excipients. Potential mechanisms and strategies to mitigate the LER phenomenon are also discussed as presented by different research groups.

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.

Biochemical analysis of leptospiral LPS explained the difference between pathogenic and non-pathogenic serogroups

Lipopolysaccharide (LPS) is the major surface antigen of Leptospira. In this study, the genes involved in the LPS biosynthesis were analyzed and compared by bioinformatics tools. Also, the chemical composition analysis of leptospiral lipopolysaccharides (LPS) extracted from 5 pathogenic serovars like Autumnalis, Australis, Ballum, Grippotyphosa, Pomona, and the nonpathogenic serovar Andamana was performed. Methods used were Limulus amebocyte lysate assay (LAL), gas chromatography-mass spectrometry (GC-MS), fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance spectroscopy (NMR). LAL assay showed a significantly higher level of endotoxicity among pathogenic serovars (~0.490 EU/mL) than that of nonpathogenic Andamana (~0.102 EU/mL). FAMES analysis showed the presence of palmitic acid (C16:0), hydroxy lauric acid (3-OH-C12:0), and oleic acid (C18:0). Palmitoleic acid (C16: 1), and 3- hydroxy palmitate (3-OH-C16:0) was detected only in pathogenic serovars. In contrast myristoleic acid (C14:1) and stearic acid (C18:0) were present in Andamana. FTIR analysis revealed C-O-C stretch of esters, 3°ROH functional groups and carbohydrate vibration range were similar among pathogenic serovars. The NMR analysis reveals similarity for 6 deoxy sugars and methyl groups of Autumnalis, Australis, and Ballum. Further, the presence of palmitoleic acid and 3-hydroxy palmitate may be the significant pathogen-associated predisposing factor. This mediates high osmolarity glycerol (HOG) mediated stress response in leptospiral LPS mediated pathogenesis.

The Lipid A from the Lipopolysaccharide of the Phototrophic Bacterium Rhodomicrobium vannielii ATCC 17100 Revisited

The structure of lipid A from lipopolysaccharide (LPS) of Rhodomicrobium vannielii ATCC 17100 (Rv) a phototrophic, budding bacterium was re-investigated using high-resolution mass spectrometry, NMR, and chemical degradation protocols. It was found that the (GlcpN)-disaccharide lipid A backbone was substituted by a GalpA residue that was connected to C-1 of proximal GlcpN. Some of this GalpA residue was β-eliminated by alkaline de-acylation, which indicated the possibility of the presence of another so far unidentified substituent at C-4 in non-stoichiometric amounts. One Manp residue substituted C-4′ of distal GlcpN. The lipid A backbone was acylated by 16:0(3-OH) at C-2 of proximal GlcpN, and by 16:0(3-OH), i17:0(3-OH), or 18:0(3-OH) at C-2′ of distal GlcpN. Two acyloxy-acyl moieties that were mainly formed by 14:0(3-O-14:0) and 16:0(3-O-22:1) occupied the distal GlcpN of lipid A. Genes that were possibly involved in the modification of Rv lipid A were compared with bacterial genes of known function. The biological activity was tested at the model of human mononuclear cells (MNC), showing that Rv lipid A alone does not significantly stimulate MNC. At low concentrations of toxic Escherichia coli O111:B4 LPS, pre-incubation with Rv lipid A resulted in a substantial reduction of activity, but, when higher concentrations of E. coli LPS were used, the stimulatory effect was increased.

Antimicrobial Peptides with Enhanced Salt Resistance and Antiendotoxin Properties

A strategy was described to design antimicrobial peptides (AMPs) with enhanced salt resistance and antiendotoxin activities by linking two helical AMPs with the Ala-Gly-Pro (AGP) hinge. Among the designed peptides, KR12AGPWR6 demonstrated the best antimicrobial activities even in high salt conditions (NaCl ~300 mM) and possessed the strongest antiendotoxin activities. These activities may be related to hydrophobicity, membrane-permeability, and α-helical content of the peptide. Amino acids of the C-terminal helices were found to affect the peptide-induced permeabilization of LUVs, the α-helicity of the designed peptides under various LUVs, and the LPS aggregation and size alternation. A possible model was proposed to explain the mechanism of LPS neutralization by the designed peptides. These findings could provide a new approach for designing AMPs with enhanced salt resistance and antiendotoxin activities for potential therapeutic applications.

Antioxidative role of propolis on LPS induced renal damage

Sepsis is a systemic infectious disease that leads to shock, organ failure, and death and requires urgent treatment. Animal model studies of sepsis and endotoxemia have revealed that antioxidant compounds prevent the progression of multi-system organ failure and reduce death rate. In the present study aimed to establish the effect of propolis, which has been proven to have antibacterial, anti-inflammatory and antioxidant activities in recent years, on lipopolysaccharide (LPS)-induced renal damage. 40 Sprague dawley rats were randomly divided into five equal groups (n = 8): Control (0.9% NaCl), LPS (30 mg/kg), propolis (250 mg/kg), propolis + LPS, and LPS + propolis. After completion of the experimental protocol, Malondialdehyde (MDA) levels were measured using blood serum samples obtained from the rats. The kidney samples of the rats were examined histopathologically. As a result, it was determined that LPS increased MDA levels in the blood serum samples and it caused histological changes in the kidney tissue such as tubular damage, mild ischemic injury, ischemic damage in the form of vacuolization, tubular epithelial vacuolization, vascular congestion, and glomerular atrophy. Contrary to these results, MDA levels of serum decreased in the propolis + LPS, and LPS + propolis groups, and also histological findings improved. These results showed that protective effect of propolis against kidney damage caused by LPS.

Inhibitory Effects of Carrageenans on Endotoxin-Induced Inflammation

The inhibitory effects of carrageenans (CRGs) on lipopolysaccharide (LPS) induced inflammation in a mouse model of endotoxemia and in complex therapy of patients with enteric infections of Salmonella etiology were studied. The atomic force microscopy (AFM) examination of LPS and its mixture with CRGs showed that the LPS morphology is significantly changed under the action of κ- and κ/β-CRGs. CRGs were able to increase the synthesis of anti-inflammatory interleukin 10 (IL-10) in vitro, and, at low concentrations, their activity in the mixture with LPS was higher. The protective effect of CRGs against Escherichia coli LPS was studied in vivo by monitoring the biochemical and pathomorphological parameters. The κ- and κ/β-CRGs and food supplement "Carrageenan-FE" increased the nonspecific resistance of mice to E. coli LPS at the expense of the inhibition of processes of thymus involution, adrenals hypertrophy, thyroid atrophy, hypercorticoidism, glycogenolysis, and lactate acidosis. The estimation of the therapeutic action of food supplement Carrageenan-FE in complex therapy of patients with enteric infections of Salmonella etiology is given. Carrageenan-FE restores the system of hemostasis and corrects some biochemical indicators and parameters in the immune systems of patients. These results allow us to hope for the practical application of CRGs for lowering the endotoxemia level in patients under the development of the infectious process caused by Gram-negative bacteria.

Ultrahigh packing density next generation microtube array membrane: A novel solution for absorption-based extracorporeal endotoxin removal device

Sepsis is a deadly disease that is widely attributed to endotoxin released by gram-negative bacterial infections often plague emergency care facilities. Conventionally antibiotics and vasopressors are used to treat this disease. Recent treatment protocol shifted to a membrane to remove the offending endotoxin monomer. Despite this shift, membrane-based devices are often extremely costly, hindering accessibility to this life saving medical device. In view of this challenges, we adopted the internally developed polysulfone (PSF) microtube array membrane alternating (MTAM-A) for use in blood sepsis treatment. PSF MTAM-A were with polymyxin B (PMB) molecules immobilized were assembled into an internally developed cartridge housing and subjected to endotoxin removal models with water and blood spiked with 100 EU/ml of endotoxin as the feed solution. Samples were derived at 15, 30, 60, and 120 min and endotoxin levels were determined with limulus amebocyte lysate assay and benchmarked against the commercially available Toraymyxin device. The PSF MTAM-A with 2.3 times the surface area was successfully fabricated and with PMB molecules immobilized, and assembled into a hemoperfusion device. Dynamic endotoxin removal test revealed and overall endotoxin removal capacity of 90% and a superior endotoxin removal efficiency that was significantly higher than that of Toraymyxin (internally conducted and reported). The data suggested that PSF MTAM-A PMB membranes could potentially be applied in future hemoperfusion devices which would be significantly more efficient, compact, and affordable; potentially making such a life-saving medical device widely available to the general public.

Mucoid and coccoid Helicobacter pylori with fast growth and antibiotic resistance

BACKGROUND

In this study, one Helicobacter pylori isolate, from gastric biopsy of a dyspeptic patient that turned into mucoid-coccoid (MC) form upon consecutive subcultures, was identified. The culturability, antibiotic resistance, and lipid contents of MC were compared with those of non-mucoid (NM) spiral H pylori.

MATERIALS AND METHODS

Mucoid-coccoid and NM H pylori were subcultured on Brucella blood agar (BBA) and incubated under aerobic and microaerobic atmospheres at 37°C. Cultures were examined for colony characteristics and bacterial morphology after 1-3 days. The isolates were identified by biochemical tests and detection of H pylori-16S rDNA. Antibiogram was performed with currently used antibiotics for H pylori eradication. Cellular lipid contents were extracted and analyzed by gas chromatography.

RESULTS

Compared with pin-pointed and glistening colonies of NM H pylori that appeared under microaerobic conditions, MC H pylori grew well in consecutive subcultures under aerobic and microaerobic atmospheres and produced white patches of mucoid colonies. MC exhibited coccoid and NM spiral morphology. Both isolates were catalase, oxidase, and urease positive and contained 16S rDNA. Compared with NM that was susceptible to almost all the antibiotics, MC was resistant to all the antibiotics. Lipid analyses showed high frequency of unsaturated fatty acids and cholesterol in MC.

CONCLUSIONS

Coccoid forms with high fatty acid and cholesterol contents that show resistance to antibiotics might resist against other stressful conditions such as gastric acidity and immune response. Moreover, mucoid property may enhance resistance of coccoids to stresses. With mucoid-coccoid lifestyle, H pylori may establish a chronic infection refractory to antimicrobial therapy.

Recent Advances in Anti-virulence Therapeutic Strategies With a Focus on Dismantling Bacterial Membrane Microdomains, Toxin Neutralization, Quorum-Sensing Interference and Biofilm Inhibition

Antimicrobial resistance constitutes one of the major challenges facing humanity in the Twenty-First century. The spread of resistant pathogens has been such that the possibility of returning to a pre-antibiotic era is real. In this scenario, innovative therapeutic strategies must be employed to restrict resistance. Among the innovative proposed strategies, anti-virulence therapy has been envisioned as a promising alternative for effective control of the emergence and spread of resistant pathogens. This review presents some of the anti-virulence strategies that are currently being developed, it will cover strategies focused on quench pathogen quorum sensing (QS) systems, disassemble of bacterial functional membrane microdomains (FMMs), disruption of biofilm formation and bacterial toxin neutralization.

Cationic Amphipathic Triazines with Potent Anti-bacterial, Anti-inflammatory and Anti-atopic Dermatitis Properties

The emergence of multi-drug resistant bacteria forces the therapeutic world into a position, where the development of new and alternative kind of antibiotics is highly important. Herein, we report the development of triazine-based amphiphilic small molecular antibacterial agents as mimics of lysine- and arginine-based cationic peptide antibiotics (CPAs). These compounds were screened against a panel of both Gram-positive and Gram-negative bacterial strains. Further, anti-inflammatory evaluation of these compounds led to the identification of four efficient compounds, DG-5, DG-6, DL-5, and DL-6. These compounds displayed significant potency against drug-resistant bacteria, including methicillin-resistant S. aureus (MRSA), multidrug-resistant P. aeruginosa (MDRPA), and vancomycin-resistant E. faecium (VREF). Mechanistic studies, including cytoplasmic membrane depolarization, confocal imaging and flow cytometry suggest that DG-5, DG-6, and DL-5 kill bacteria by targeting bacterial membrane, while DL-6 follows intracellular targeting mechanism. We also demonstrate that these molecules have therapeutic potential by showing the efficiency of DG-5 in preventing the lung inflammation of lipopolysaccharide (LPS)-induced acute lung injury (ALI) mouse model. More interestingly, DL-6 exhibited impressive potency on atopic dermatitis (AD)-like skin lesions in BALB/c mice model by suppressing pro-inflammatory cytokines. Collectively, these results suggest that they can serve a new class of antimicrobial, anti-inflammatory and anti-atopic agents with promising therapeutic potential.

Highly homogenous tri-acylated S-LPS acts as a novel clinically applicable vaccine against Shigella flexneri 2a infection

Shigellosis, a major cause of diarrhea worldwide, exhibits high morbidity and mortality in children. Specificity of Shigella immunity is determined by the structure of the main protective O-antigen polysaccharide component incorporated into the lipopolysaccharide (LPS) molecule. Endotoxicity, however, precludes LPS clinical use. Thus, there is still no vaccine against the most prevalent shigellosis species (serotype S. flexneri 2a), despite ongoing efforts focused on inducing serotype-specific immunity. As LPS is highly heterogenous, we hypothesized that more homogenous pools of LPS might be less toxic. We developed a method to generate a homogenous S. flexneri 2a LPS subfraction, Ac₃-S-LPS, containing long chain O-specific polysaccharide (S-LPS) and mainly tri-acylated lipid A, with no penta- and hexa-acylated, and rare tetra-acylated lipid A. Ac₃-S-LPS had dramatically reduced pyrogenicity and protected guinea pigs from shigellosis. In volunteers, 50 µg of injected Ac₃-S-LPS vaccine was safe, with low pyrogenicity, no severe and few minor adverse events, and did not induce pro-inflammatory cytokines. In spite of the profound lipid A modification, the vaccine induced a prevalence of IgG and IgA antibodies. Thus, we have developed the first safe immunogenic LPS-based vaccine candidate for human administration. Homogenous underacetylated LPSs may also be useful for treating other LPS-driven human diseases. Clinical trial registry: http://grls.rosminzdrav.ru/.

Endotoxin rapidly desensitizes the gonads to kisspeptin-induced luteinizing hormone release in male Siberian hamsters (Phodopus sungorus)

Activation of the immune system induces rapid reductions in hypothalamic-pituitary-gonadal (HPG) axis activity, which in turn decreases secretion of sex steroids. This response is likely adaptive for survival by temporarily inhibiting reproduction to conserve energy; however, the physiological mechanisms controlling this response remain unclear. The neuropeptide kisspeptin is a candidate to mediate the decrease in sex hormones seen during sickness through its key regulation of the HPG axis. In this study, the effects of acute immune activation on the response to kisspeptin were assessed in male Siberian hamsters (Phodopus sungorus). Specifically, an immune response was induced in animals by a single treatment of lipopolysaccharide (LPS), and reproductive hormone concentrations were determined in response to subsequent injections of exogenous kisspeptin. Saline-treated controls showed a robust increase in circulating testosterone in response to kisspeptin; however, this response was blocked in LPS-treated animals. Circulating luteinizing hormone (LH) levels were elevated in response to kisspeptin in both LPS- and saline-treated groups and, thus, were unaffected by LPS treatment, suggesting gonad-level inhibition of testosterone release despite central HPG activation. In addition, blockade of glucocorticoid receptors by mifepristone did not attenuate the LPS-induced inhibition of testosterone release, suggesting that circulating glucocorticoids do not mediate this phenomenon. Collectively, these findings reveal that acute endotoxin exposure rapidly renders the gonads less sensitive to HPG stimulation, thus effectively inhibiting sex hormone release. More broadly, these results shed light on the effects of immune activation on the HPG axis and help elucidate the mechanisms controlling energy allocation and reproduction.

LBP rs2232618 polymorphism contributes to risk of sepsis after trauma

Background

Previous study revealed that rs2232618 polymorphism (Phe436Leu) within LBP gene is a functional variant and associated with susceptibility of sepsis in traumatic patients. Our aim was to confirm the reported association by enlarging the population sample size and perform a meta-analysis to find additional evidence.

Methods

Traumatic patients from Southwest (n = 1296) and Southeast (n = 445) of China were enrolled in our study. After genotyping, the relationship between rs2232618 and the risk of sepsis was analyzed. Furthermore, we proceeded with a comprehensive literature search and meta-analysis to determine whether the rs2232618 polymorphism conferred susceptibility to sepsis.

Results

Significance correlation was observed between rs2232618 and risk of sepsis in Southwest patients (P = 0.002 for the dominant model, P = 0.006 for the recessive model). The association was confirmed in Southeast cohort (P = 0.005 for the dominant model) and overall combined cohorts (P = 4.5 × 10^-4, P = 0.041 for the dominant and recessive model). Multiple logistical regression analyses suggested that rs2232618 polymorphism was related to higher risk of sepsis (OR = 1.77, 95% CI = 1.26-2.48, P = 0.001 in Southwest patients; OR = 2.11, 95% CI = 1.24-3.58, P = 0.006 in Southeast cohort; OR = 1.54, 95% CI = 1.34-2.08, P = 0.006 in overall cohort). Furthermore, meta-analysis of four studies (including the present study) confirmed that rs2232618 within LBP increased the risk of sepsis (OR = 1.75, P < 0.001 for the dominant model; OR = 6.08, P = 0.003 for the recessive model; OR = 2.72, P < 0.001 for the allelic model).

Conclusions

The results from our replication study and meta-analysis provided firm evidence that rs2232618T allele significantly increased the risk of sepsis.

Investigation into Cellular Glycolysis for the Mechanism Study of Energy Metabolism Disorder Triggered by Lipopolysaccharide

Lipopolysaccharide (LPS) is the main virulence factor of Gram-negative bacteria, which can incite inflammation in tissues by inducing cells to secrete a variety of proinflammatory mediators, including cytokines, chemokines, interleukins, and prostaglandins. Herein, we chose LPS as an inducer to establish an inflammatory model of HeLa cells, and explored the effects of LPS on energy metabolism. We treated HeLa cells with different concentrations (0, 0.4, 1.0, 2.0, 4.0, and 6.0 μg/mL) of LPS for 24 h, and explored its effects on intercellular adenosine triphosphate (ATP) levels, intercellular nitrous oxide (NO) content, mitochondrial functions, and enzyme activities related to energy metabolism. Furthermore, we used metabonomics to study the metabolites that participated in energy metabolism. We found a positive correlation between LPS concentrations and intracellular ATP levels. In addition, LPS increased intracellular NO production, altered mitochondrial functions, strengthened glycolytic enzyme activities, and changed metabolites related to energy metabolism. Hence, in this study, we showed that LPS can strengthen energy metabolism by enhancing glycolysis, which could be used as an early diagnostic biomarker or a novel therapeutic target for inflammation-associated cancers.

Bradyrhizobium Lipid A: Immunological Properties and Molecular Basis of Its Binding to the Myeloid Differentiation Protein-2/Toll-Like Receptor 4 Complex

Lipopolysaccharides (LPS) are potent activator of the innate immune response through the binding to the myeloid differentiation protein-2 (MD-2)/toll-like receptor 4 (TLR4) receptor complexes. Although a variety of LPSs have been characterized so far, a detailed molecular description of the structure–activity relationship of the lipid A part has yet to be clarified. Photosynthetic Bradyrhizobium strains, symbiont of Aeschynomene legumes, express distinctive LPSs bearing very long-chain fatty acids with a hopanoid moiety covalently linked to the lipid A region. Here, we investigated the immunological properties of LPSs isolated from Bradyrhizobium strains on both murine and human immune systems. We found that they exhibit a weak agonistic activity and, more interestingly, a potent inhibitory effect on MD-2/TLR4 activation exerted by toxic enterobacterial LPSs. By applying computational modeling techniques, we also furnished a plausible explanation for the Bradyrhizobium LPS inhibitory activity at atomic level, revealing that its uncommon lipid A chemical features could impair the proper formation of the receptorial complex, and/or has a destabilizing effect on the pre-assembled complex itself.

Cyanobacteria Scytonema javanicum and Scytonema ocellatum Lipopolysaccharides Elicit Release of Superoxide Anion, Matrix-Metalloproteinase-9, Cytokines and Chemokines by Rat Microglia In Vitro

Cosmopolitan Gram-negative cyanobacteria may affect human and animal health by contaminating terrestrial, marine and freshwater environments with toxins, such as lipopolysaccharide (LPS). The cyanobacterial genus Scytonema (S) produces several toxins, but to our knowledge the bioactivity of genus Scytonema LPS has not been investigated. We recently reported that cyanobacterium Oscillatoria sp. LPS elicited classical and alternative activation of rat microglia in vitro. Thus, we hypothesized that treatment of brain microglia in vitro with either cyanobacteria S. javanicum or S. ocellatum LPS might stimulate classical and alternative activation with concomitant release of superoxide anion (O₂^-), matrix metalloproteinase-9 (MMP-9), cytokines and chemokines. Microglia were isolated from neonatal rats and treated in vitro with either S. javanicum LPS, S. ocellatum LPS, or E. coli LPS (positive control), in a concentration-dependent manner, for 18 h at 35.9 °C. We observed that treatment of microglia with either E. coli LPS, S. javanicum or S. ocellatum LPS generated statistically significant and concentration-dependent O₂^-, MMP-9 and pro-inflammatory cytokines IL-6 and TNF-α, pro-inflammatory chemokines MIP-2/CXCL-2, CINC-1/CXCL-1 and MIP-1α/CCL3, and the anti-inflammatory cytokine IL-10. Thus, our results provide experimental support for our working hypothesis because both S. javanicum and S. ocellatum LPS elicited classical and alternative activation of microglia and concomitant release of O₂^-, MMP-9, cytokines and chemokines in a concentration-dependent manner in vitro. To our knowledge this is the first report on the toxicity of cyanobacteria S. javanicum and S. ocellatum LPS to microglia, an immune cell type involved in neuroinflammation and neurotoxicity in the central nervous system.

Progress in the synthesis and biological evaluation of lipid A and its derivatives

Lipid A is one of the core structures of bacterial lipopolysaccharides (LPSs), and it is mainly responsible for the strong immunostimulatory activities of LPS through interactions with the Toll-like receptors and other molecules in the human immune system. To obtain structurally homogeneous and well-defined lipid As and its derivatives in quantities meaningful for various biological studies and applications, their chemical synthesis has become a focal point. This review has provided a survey of significant progresses made in the synthesis of lipid A, and its derivatives that carry diverse saturated and unsaturated lipids, have the phosphate group at its reducing end replaced with a more stable phosphate or carboxyl group, or lack the reducing end phosphate or both phosphate groups, as well as progresses in the synthesis of LPS analogs and other lipid A conjugates. These synthetic molecules have facilitated the elucidation of the structure-activity relationships of lipid A useful for the design and development of lipid A based therapeutics, such as those utilized to treat sepsis, and other medical applications, for example the use of monophosphoryl lipid A as a carrier molecule for the study of fully synthetic self-adjuvanting conjugate vaccines. These topics are also briefly covered in the current review.

Diet, Gut Microbiota, and Vitamins D + A in Multiple Sclerosis

Central to the understanding of the relationships between diet, gut microbiota, and vitamins D and A in multiple sclerosis is low-grade inflammation, which is involved in all chronic inflammatory diseases and is influenced by each of the above effectors. We show that food components have either proinflammatory or anti-inflammatory effects and influence both the human metabolism (the "metabolome") and the composition of gut microbiota. Hypercaloric, high-animal-fat Western diets favor anabolism and change gut microbiota composition towards dysbiosis. Subsequent intestinal inflammation leads to leakage of the gut barrier, disruption of the blood-brain barrier, and neuroinflammation. Conversely, a vegetarian diet, rich in fiber, is coherent with gut eubiosis and a healthy condition. Vitamin D levels, mainly insufficient in a persistent low-grade inflammatory status, can be restored to optimal values only by administration of high amounts of cholecalciferol. At its optimal values (>30 ng/ml), vitamin D requires vitamin A for the binding to the vitamin D receptor and exert its anti-inflammatory action. Both vitamins must be supplied to the subjects lacking vitamin D. We conclude that nutrients, including the nondigestible dietary fibers, have a leading role in tackling the low-grade inflammation associated with chronic inflammatory diseases. Their action is mediated by gut microbiota and any microbial change induced by diet modifies host-microbe interactions in a consequent way, to improve the disease or worsen it.

Encapsulated Hsp70 decreases endotoxin-induced production of ROS and TNFα in human phagocytes

Human heat shock protein Hsp70 was experimentally inserted into polyelectrolyte microcapsules. Encapsulated recombinant Hsp70 was studied in terms of its effects on neutrophil apoptosis, the production of reactive oxygen species, and the secretion of tumor necrosis factor alpha by promonocytic THP-1 cells. It was found that encapsulated Hsp70 effectively inhibits neutrophil apoptosis, unlike free exogenous protein used in solution. In THP-1 cells, encapsulated and free Hsp70 reduced LPS-induced tumor necrosis factor alpha production with a similar efficiency. Encapsulated Hsp70 reduces LPS-induced reactive oxygen species production by neutrophils in the course of its release from the microcapsules but not as much as free Hsp70. Thus, the polyelectrolyte microcapsules can be used as containers for the effective delivery of Hsp70 to neutrophils and monocytes to significantly improve the functioning of the innate immune system.

An aptamer-based fluorescence probe for facile detection of lipopolysaccharide in drinks

An alternative fluorescence strategy for specific and convenient detection of lipopolysaccharide in drink was developed.

Carrageenans effect on neutrophils alone and in combination with LPS in vitro

Influence of sulfated red algal polysaccharides (κ-, λ-, and κ/β-carrageenans) and degraded derivative of κ/β-carrageenan on neutrophils/monocytes activation alone and in combination with lipopolysaccharide was investigated by means of determination of reactive oxygen species production, latex microparticles engulfment, total and extracellular myeloperoxidase induction and the analysis of silhouette and contour two-dimensional images of flattened cells. Carrageenans alone can activate neutrophils with much less potency than lipopolysaccharide (LPS) and the sulfation degree of carrageenans stipulates high activity in this role. On the other hand, carrageenans especially with low contents of sulfate groups are able to interfere with LPS in vitro resulting in reducing inter- and intracellular activation of neutrophils killing mechanisms. Further research is necessary to relate these findings to actions on the whole animal or human in vivo. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1603-1609, 2016.

Comparative analysis of lipopolysaccharides of pathogenic and intermediately pathogenic Leptospira species

Background

Lipopolysaccharides (LPS) are complex, amphipathic biomolecules that constitute the major surface component of Gram-negative bacteria. Leptospira, unlike other human-pathogenic spirochetes, produce LPS, which is fundamental to the taxonomy of the genus, involved in host-adaption and also the target of diagnostic antibodies. Despite its significance, little is known of Leptospira LPS composition and carbohydrate structure among different serovars.

Results

LPS from Leptospira interrogans serovar Copenhageni strain L1-130, a pathogenic species, and L. licerasiae serovar Varillal strain VAR 010, an intermediately pathogenic species, were studied. LPS prepared from aqueous and phenol phases were analyzed separately. L. interrogans serovar Copenhageni has additional sugars not found in L. licerasiae serovar Varillal, including fucose (2.7 %), a high amount of GlcNAc (12.3 %), and two different types of dideoxy HexNAc. SDS-PAGE indicated that L. interrogans serovar Copenhageni LPS had a far higher molecular weight and complexity than that of L. licerasiae serovar Varillal. Chemical composition showed that L. interrogans serovar Copenhageni LPS has an extended O-antigenic polysaccharide consisting of sugars, not present in L. licerasiae serovar Varillal. Arabinose, xylose, mannose, galactose and L-glycero-D-mannoheptose were detected in both the species. Fatty acid analysis by gas chromatography–mass spectrometry (GC-MS) showed the presence of hydroxypalmitate (3-OH-C16:0) only in L. interrogans serovar Copenhageni. Negative staining electron microscopic examination of LPS showed different filamentous morphologies in L. interrogans serovar Copenhageni vs. L. licerasiae serovar Varillal.

Conclusions

This comparative biochemical analysis of pathogenic and intermediately pathogenic Leptospira LPS reveals important carbohydrate and lipid differences that underlie future work in understanding the mechanisms of host-adaptation, pathogenicity and vaccine development in leptospirosis.

Micro-concentration Lipopolysaccharide as a Novel Stimulator of Megakaryocytopoiesis that Synergizes with IL-6 for Platelet Production

Lipopolysaccharide (LPS) induces platelet activation and enhances platelet sensitivity to aggregation, which might alter platelet counts. We found that serial doses of micro-concentration LPS significantly increased the platelet count in mice treated with kanamycin, along with increased expression of IL-6 compared with IL-3 and TPO in megakaryocytes obtained from the mouse bone morrow following LPS administration. Furthermore, LPS at lower levels ranging plus IL-6 effectively stimulated CFU-MK formation and increased CD41 expression and megakaryocyte polyploidization. Meanwhile, there was a sustained rise in the percentage of reticulated platelets in the whole blood in response to low-dosage LPS combined with IL-6. In vivo experiments also demonstrated that the administration of LPS combined with IL-6 substantially enhanced the number of circulating platelets in normal and thrombocytopenic mice. Notably, the optimal LPS concentration in combination with IL-6 might be a novel stimulator of TLR4 and IL-6R expression in Dami cell lines, which initially occurs through TLR4-IL-6R crosstalk and then involves the activation of NF-κB and phosphorylation of p38 MAPK. These data suggest a new paradigm for the regulation of megakaryocytopoiesis and platelet production via a synergistic effect of LPS and IL-6, which has the potential to be used for the design of new therapies.

Ultrashort Antimicrobial Peptides with Antiendotoxin Properties

Release of lipopolysaccharide (LPS) (endotoxin) from bacteria into the bloodstream may cause serious unwanted stimulation of the host immune system. Some but not all antimicrobial peptides can neutralize LPS-stimulated proinflammatory responses. Salt resistance and serum stability of short antimicrobial peptides can be boosted by adding β-naphthylalanine to their termini. Herein, significant antiendotoxin effects were observed in vitro and in vivo with the β-naphthylalanine end-tagged variants of the short antimicrobial peptides S1 and KWWK.

Biofouling of reverse osmosis membranes: positively contributing factors of Sphingomonas

In the present study, we investigate the possible contribution of Sphingomonas spp. glycosphingolipids (GSL) and its extracellular polymeric substances (EPS) to the initial colonization and development of biofilm bodies on reverse osmosis (RO) membranes. A combination of an RO cross-flow membrane lab unit, a quartz crystal microbalance with dissipation (QCM-D), and a rear stagnation point flow (RSPF) system with either model bacteria (Sphingomonas wittichii, Escherichia coli, and Pseudomonas aeruginosa) or vesicles made of the bacterial GSL or LPS was used. Results showed noticeable differences in the adhesion LPS versus GSL vesicles in the QCM-D, with the latter exhibiting 50% higher adhesion to polyamide coated crystals (mimicking an RO membrane surface). A similar trend was observed for EPS extracted from S. wittichii, when compared to the adhesion tendency of EPS extracted from P. aeruginosa. By applying the whole-cell approach in the RO lab unit, the cumulative impact of S. wittichii cells composing GSL and probably their EPS reduced the permeate flux during bacterial accumulation on the membrane surface. Experiments were conducted with the same amount of Sphingomonas spp. or Escherichia coli cells resulting in a two times greater flux decline in the presence of S. wittichii. The distinct effects of Sphingomonas spp. on RO membrane biofouling are likely a combination of GSL presence (known for enhancing adhesion when compared to non-GSL containing bacteria) and the EPS contributing to the overall strength of the biofilm matrix.

Impact of plasmids, including those encodingVirB4/D4 type IV secretion systems, on Salmonella enterica serovar Heidelberg virulence in macrophages and epithelial cells

Salmonella enterica serovar Heidelberg (S. Heidelberg) can cause foodborne illness in humans following the consumption of contaminated meat and poultry products. Recent studies from our laboratory have demonstrated that certain S. Heidelberg isolated from food-animal sources harbor multiple transmissible plasmids with genes that encode antimicrobial resistance, virulence and a VirB4/D4 type-IV secretion system. This study examines the potential role of these transmissible plasmids in bacterial uptake and survival in intestinal epithelial cells and macrophages, and the molecular basis of host immune system modulation that may be associated with disease progression. A series of transconjugant and transformant strains were developed with different combinations of the plasmids to determine the roles of the individual and combinations of plasmids on virulence. Overall the Salmonella strains containing the VirB/D4 T4SS plasmids entered and survived in epithelial cells and macrophages to a greater degree than those without the plasmid, even though they carried other plasmid types. During entry in macrophages, the VirB/D4 T4SS encoding genes are up-regulated in a time-dependent fashion. When the potential mechanisms for increased virulence were examined using an antibacterial Response PCR Array, the strain containing the T4SS down regulated several host innate immune response genes which likely contributed to the increased uptake and survival within macrophages and epithelial cells.

The sugar 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) as a characteristic component of bacterial endotoxin — a review of its biosynthesis, function, and placement in the lipopolysaccharide core

The sugar 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) is a characteristic component of bacterial lipopolysaccharide (LPS, endotoxin). It connects the carbohydrate part of LPS with C6 of glucosamine or 2,3-diaminoglucose of lipid A by acid-labile α-ketosidic linkage. The number of Kdo units present in LPS, the way they are connected, and the occurrence of other substituents (P, PEtn, PPEtn, Gal, or β-l-Ara4N) account for structural diversity of the inner core region of endotoxin. In a majority of cases, Kdo is crucial to the viability and growth of bacterial cells. In this paper, the biosynthesis of Kdo and the mechanism of its incorporation into the LPS structure, as well as the location of this unique component in the endotoxin core structures, have been described.

[Usefulness of haemoperfusion in the treatment of the severe septic patient: an update]

Haemoperfusion is an extracorporeal technique that removes endotoxin and/or inflammatory mediators by means of an adsorptive mechanism during the passage of the blood through a porous filter. Most of the studies in the literature use polymyxin B as the adsorptive agent. This treatment is based on the assumption that the removal of endotoxin and inflammatory mediators from the circulation attenuates the inflammatory response in sepsis. This review summarizes the theoretical basis, and the experimental and clinical results published to date with the use of haemoperfusion. Although most of the studies show positive results, some doubts have arisen about the suitability of the methods described (small number of cases, low quality of the experimental design, and excessive mortality in the control groups). There are also some inconsistencies regarding the theoretical basis of its use (lack of positive effects after the removal of endotoxin from the circulation using alternative mechanisms, discrepancies regarding the best moment to initiate the therapy, unexplained beneficial effects in the absence of increased endotoxin levels). It is the opinion of the authors that haemoperfusion represents a promising therapy for the treatment of sepsis, but consider that its usefulness requires confirmation in well designed studies before being included in protocols.

PPARγ activation prevents impairments in spatial memory and neurogenesis following transient illness

The detrimental effects of illness on cognition are familiar to virtually everyone. Some effects resolve quickly while others may linger after the illness resolves. We found that a transient immune response stimulated by lipopolysaccharide (LPS) compromised hippocampal neurogenesis and impaired hippocampus-dependent spatial memory. The immune event caused an ∼50% reduction in the number of neurons generated during the illness and the onset of the memory impairment was delayed and coincided with the time when neurons generated during the illness would have become functional within the hippocampus. Broad spectrum non-steroidal anti-inflammatory drugs attenuated these effects but selective Cox-2 inhibition was ineffective while PPARγ activation was surprisingly effective at protecting both neurogenesis and memory from the effects of LPS-produced transient illness. These data may highlight novel mechanisms behind chronic inflammatory and neuroinflammatory episodes that are known to compromise hippocampus-dependent forms of learning and memory.

Endotoxins-the invisible companion in biomaterials research

Metal implants and polymeric devices for the application in the clinical treatment of orthopedic tissue injuries are increasingly coated with bioactive biomaterials derived from natural substances to induce desirable biological effects. Many metals and polymers used in biomaterials research show high affinity for endotoxins, which are abundant in the environment. Endotoxin contamination is indicated in the pathology of periodontitis and aseptic implant loosening, but may also affect the evaluation of a biomaterial's bioactivity by inducing strong inflammatory reactions. In this review, we discuss the high affinity of three commonly used implant biomaterials for endotoxins and how the contamination can affect the outcome of the orthopedic fixation. The chemical nature of bacterial endotoxins and some of the clinical health implications are described, as this knowledge is critically important to tackle the issues associated with the measurement and removal of endotoxins from medical devices. Commonly used methods for endotoxin testing and removal from natural substances are examined and the lack of standard guidelines for the in vitro evaluation of biomaterials is discussed.

Antibody WN1 222-5 mimics Toll-like receptor 4 binding in the recognition of LPS

Escherichia coli infections, a leading cause of septic shock, remain a major threat to human health because of the fatal action to endotoxin (LPS). Therapeutic attempts to neutralize endotoxin currently focus on inhibiting the interaction of the toxic component lipid A with myeloid differentiating factor 2, which forms a trimeric complex together with Toll-like receptor 4 to induce immune cell activation. The 1.73-Å resolution structure of the unique endotoxin-neutralizing protective antibody WN1 222-5 in complex with the core region shows that it recognizes LPS of all E. coli serovars in a manner similar to Toll-like receptor 4, revealing that protection can be achieved by targeting the inner core of LPS and that recognition of lipid A is not required. Such interference with Toll-like receptor complex formation opens new paths for antibody sepsis therapy independent of lipid A antagonists.

Global effect of interleukin-10 on the transcriptional profile induced by Neisseria meningitidis in human monocytes

In meningococcal septic shock, the dominant inducer of inflammation is lipopolysaccharide (LPS) in the outer membrane of Neisseria meningitidis, while interleukin-10 (IL-10) is the principal anti-inflammatory cytokine. We have used microarrays and Ingenuity Pathway Analysis to study the global effects of IL-10 on gene expression induced by N. meningitidis, after exposure of human monocytes (n = 5) for 3 h to N. meningitidis (10(6) cells/ml), recombinant human IL-10 (rhIL-10) (25 ng/ml), and N. meningitidis combined with rhIL-10. N. meningitidis and IL-10 differentially expressed 3,579 and 648 genes, respectively. IL-10 downregulated 125 genes which were upregulated by N. meningitidis, including NLRP3, the key molecule of the NLRP3 inflammasome. IL-10 also upregulated 270 genes which were downregulated by N. meningitidis, including members of the leukocyte immunuglobulin-like receptor (LIR) family. Fifty-three genes revealed a synergistically increased expression when N. meningitidis and IL-10 were combined. AIM2 (the principal molecule of the AIM2 inflammasome) was among these genes (fold change [FC], 18.3 versus 7.4 and 9.4 after stimulation by N. meningitidis and IL-10, respectively). We detected reduced concentrations (92% to 40%) of six cytokines (IL-1b, IL-6, IL-8, tumor necrosis factor alpha [TNF-α], macrophage inflammatory protein alpha [MIP-α], MIP-β) in the presence of IL-10, compared with concentrations with stimulation by N. meningitidis alone. Our data analysis of the effects of IL-10 on gene expression induced by N. meningitidis suggests that high plasma levels of IL-10 in meningococcal septic shock plasma may have a profound effect on a variety of functions and cellular processes in human monocytes, including cell-to-cell signaling, cellular movement, cellular development, antigen presentation, and cell death.

Genomic basis of endosymbiont-conferred protection against an insect parasitoid

Bacterial endosymbionts exert a variety of beneficial effects on insect hosts. In pea aphids (Acyrthosiphon pisum), several inherited endosymbiont species protect their hosts against parasitoid wasps, which are major natural enemies. However, strains of these symbiont species vary in their ability to confer protection against parasitoids, with some conferring almost complete protection and others conferring almost none. In this study, two strains of the endosymbiont Regiella insecticola (R. insecticola 5.15 and R. insecticola LSR1) were found to differ in ability to protect pea aphids attacked by the parasitoid Aphidius ervi. Parasitism trials reveal that R. insecticola 5.15, but not R. insecticola LSR1, significantly reduced parasitoid success and increased aphid survivorship. To address the potential genetic basis of protection conferred by R. insecticola 5.15 we sequenced the genome of this symbiont strain, and then compared its gene repertoire with that of the already sequenced nonprotective strain R. insecticola LSR1. We identified striking differences in gene sets related to eukaryote pathogenicity. The protective strain R. insecticola 5.15 encoded five categories of pathogenicity factors that were missing or inactivated in R. insecticola LSR1. These included genes encoding the O-antigen biosynthetic pathway, an intact Type 1 Secretion System and its secreted RTX toxins, an intact SPI-1 Type 3 Secretion System and its effectors, hemin transport, and the two-component system PhoPQ. These five pathogenicity factors and translocation systems are hypothesized to collectively play key roles in the endosymbiont's virulence against parasitoids, resulting in aphid protection. Mechanisms through which these factors may target parasitoids are discussed.

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.

Subversion of innate and adaptive immune activation induced by structurally modified lipopolysaccharide from Salmonella typhimurium

Salmonella are successful pathogens that infect millions of people every year. During infection, Salmonella typhimurium changes the structure of its lipopolysaccharide (LPS) in response to the host environment, rendering bacteria resistant to cationic peptide lysis in vitro. However, the role of these structural changes in LPS as in vivo virulence factors and their effects on immune responses and the generation of immunity are largely unknown. We report that modified LPS are less efficient than wild-type LPS at inducing pro-inflammatory responses. The impact of this LPS-mediated subversion of innate immune responses was demonstrated by increased mortality in mice infected with a non-lethal dose of an attenuated S. typhimurium strain mixed with the modified LPS moieties. Up-regulation of co-stimulatory molecules on antigen-presenting cells and CD4(+) T-cell activation were affected by these modified LPS. Strains of S. typhimurium carrying structurally modified LPS are markedly less efficient at inducing specific antibody responses. Immunization with modified LPS moiety preparations combined with experimental antigens, induced an impaired Toll-like receptor 4-mediated adjuvant effect. Strains of S. typhimurium carrying structurally modified LPS are markedly less efficient at inducing immunity against challenge with virulent S. typhimurium. Hence, changes in S. typhimurium LPS structure impact not only on innate immune responses but also on both humoral and cellular adaptive immune responses.

Outer membrane protein X (Ail) contributes to Yersinia pestis virulence in pneumonic plague and its activity is dependent on the lipopolysaccharide core length

Yersinia pestis, the causative agent of plague, is one of the most virulent microorganisms known. The outer membrane protein X (OmpX) in Y. pestis KIM is required for efficient bacterial adherence to and internalization by cultured HEp-2 cells and confers resistance to human serum. Here, we tested the contribution of OmpX to disease progression in the fully virulent Y. pestis CO92 strain by engineering a deletion mutant and comparing its ability in mediating pneumonic plague to that of the wild type in two animal models. The deletion of OmpX delayed the time to death up to 48 h in a mouse model and completely attenuated virulence in a rat model of disease. All rats challenged with 1 × 10(8) CFU of the ompX mutant survived, compared to the 50% lethal dose (LD50) of 1.2 × 10(3) CFU for the wild-type strain. Because murine serum is not bactericidal for the ompX mutant, the mechanism underlying the delay in time to death in mice was attributed to loss of adhesion/internalization properties but not serum resistance. The rat model, which is most similar to humans, highlighted the critical role of serum resistance in disease. To resolve conflicting evidence for the role of Y. pestis lipopolysaccharide (LPS) and OmpX in serum resistance, ompX was cloned into Escherichia coli D21 and three isogenic derivatives engineered to have progressively truncated LPS core saccharides. OmpX-mediated serum resistance, adhesiveness, and invasiveness, although dependent on LPS core length, displayed these functions in E. coli, independently of other Yersinia proteins and/or LPS. Also, autoaggregation was required for efficient OmpX-mediated adhesiveness and internalization but not serum resistance.

New antiseptic peptides to protect against endotoxin-mediated shock

Systemic bacterial infections are associated with high mortality. The access of bacteria or constituents thereof to systemic circulation induces the massive release of immunomodulatory mediators, ultimately causing tissue hypoperfusion and multiple-organ failure despite adequate antibiotic treatment. Lipid A, the "endotoxic principle" of bacterial lipopolysaccharide (LPS), is one of the major bacterial immunostimuli. Here we demonstrate the biological efficacy of rationally designed new synthetic antilipopolysaccharide peptides (SALPs) based on the Limulus anti-LPS factor for systemic application. We show efficient inhibition of LPS-induced cytokine release and protection from lethal septic shock in vivo, whereas cytotoxicity was not observed under physiologically relevant conditions and concentrations. The molecular mechanism of LPS neutralization was elucidated by biophysical techniques. The lipid A part of LPS is converted from its "endotoxic conformation," the cubic aggregate structure, into an inactive multilamellar structure, and the binding affinity of the peptide to LPS exceeds those of known LPS-binding proteins, such as LPS-binding protein (LBP). Our results thus delineate a novel therapeutic strategy for the clinical management of patients with septic shock.

Altered linkage of hydroxyacyl chains in lipid A of Campylobacter jejuni reduces TLR4 activation and antimicrobial resistance

Modification of the lipid A moiety of bacterial lipopolysaccharide influences cell wall properties, endotoxic activity, and bacterial resistance to antimicrobial peptides. Known modifications are variation in the number or length of acyl chains and/or attached phosphoryl groups. Here we identified two genes (gnnA and gnnB) in the major foodborne pathogen Campylobacter jejuni that enable the synthesis of a GlcN3N precursor UDP 2-acetamido-3-amino-2,3-dideoxy-alpha-D-glucopyranose (UDP-GlcNAc3N) in the lipid A backbone. Mass spectrometry of purified lipooligosaccharide verified that the gene products facilitate the formation of a 2,3-diamino-2,3-dideoxy-D-glucose (GlcN3N) disaccharide lipid A backbone when compared with the beta-1'-6-linked D-glucosamine (GlcN) disaccharide observed in Escherichia coli lipid A. Functional assays showed that inactivation of the gnnA or gnnB gene enhanced the TLR4-MD2-mediated NF-kappaB activation. The mutants also displayed increased susceptibility to killing by the antimicrobial peptides polymyxin B, colistin and the chicken cathelicidin-1. The gnnA and gnnB genes are organized in one operon with hemH, encoding a ferrochelatase catalyzing the last step in heme biosynthesis. These results indicate that lipid A modification resulting in amide-linked acyl chains in the lipid A is an effective mechanism to evade activation of the innate host defense and killing by antimicrobial peptides.

Inflammatory stress and idiosyncratic hepatotoxicity: hints from animal models

Adverse drug reactions (ADRs) present a serious human health problem. They are major contributors to hospitalization and mortality throughout the world (Lazarou et al., 1998; Pirmohamed et al., 2004). A small fraction (less than 5%) of ADRs can be classified as "idiosyncratic." Idiosyncratic ADRs (IADRs) are caused by drugs with diverse pharmacological effects and occur at various times during drug therapy. Although IADRs affect a number of organs, liver toxicity occurs frequently and is the primary focus of this review. Because of the inconsistency of clinical data and the lack of experimental animal models, how IADRs arise is largely undefined. Generation of toxic drug metabolites and induction of specific immunity are frequently cited as causes of IADRs, but definitive evidence supporting either mechanism is lacking for most drugs. Among the more recent hypotheses for causation of IADRs is that inflammatory stress induced by exogenous or endogenous inflammagens is a susceptibility factor. In this review, we give a brief overview of idiosyncratic hepatotoxicity and the inflammatory response induced by bacterial lipopolysaccharide. We discuss the inflammatory stress hypothesis and use as examples two drugs that have caused IADRs in human patients: ranitidine and diclofenac. The review focuses on experimental animal models that support the inflammatory stress hypothesis and on the mechanisms of hepatotoxic response in these models. The need for design of epidemiological studies and the potential for implementation of inflammation interaction studies in preclinical toxicity screening are also discussed briefly.