A synthetic peptide derived from bactericidal/permeability-increasing protein neutralizes endotoxin in vitro and in vivo

Progress towards the clinical use of antimicrobial peptides: challenges and opportunities

INTRODUCTION

To overcome the challenge of multidrug resistance, natural and synthetic peptides are candidates to become the basis of innovative therapeutics, featuring diverse mechanisms of action. Traditionally, the time elapsed from medical discoveries to their application is long. The urgency derived from the emergence of antibiotic resistance recommends an acceleration of research to put the new weapons in the hands of clinicians.

AREAS COVERED

This narrative review introduces ideas and suggestions of new strategies that may be used as a basis upon which to recommend reduced development times and to facilitate the arrival of new molecules in the fight against microbes.

EXPERT OPINION

Although studies on new innovative antimicrobial treatments are being conducted, sooner rather than later, more clinical trials, preclinical and translational research are needed to promote the development of innovative antimicrobial treatments for multidrug resistant infections. The situation is worrying, no less than that generated by pandemics such as the ones we have just experienced and conflicts such as world wars. Although from the point of view of human perception, resistance to antibiotics may not seem as serious as these other situations, it is possibly the hidden pandemic that most jeopardizes the future of medicine.

Heterogeneity of Lipopolysaccharide as Source of Variability in Bioassays and LPS-Binding Proteins as Remedy

Lipopolysaccharide (LPS), also referred to as endotoxin, is the major component of Gram-negative bacteria's outer cell wall. It is one of the main types of pathogen-associated molecular patterns (PAMPs) that are known to elicit severe immune reactions in the event of a pathogen trespassing the epithelial barrier and reaching the bloodstream. Associated symptoms include fever and septic shock, which in severe cases, might even lead to death. Thus, the detection of LPS in medical devices and injectable pharmaceuticals is of utmost importance. However, the term LPS does not describe one single molecule but a diverse class of molecules sharing one common feature: their characteristic chemical structure. Each bacterial species has its own pool of LPS molecules varying in their chemical composition and enabling the aggregation into different supramolecular structures upon release from the bacterial cell wall. As this heterogeneity has consequences for bioassays, we aim to examine the great variability of LPS molecules and their potential to form various supramolecular structures. Furthermore, we describe current LPS quantification methods and the LPS-dependent inflammatory pathway and show how LPS heterogeneity can affect them. With the intent of overcoming these challenges and moving towards a universal approach for targeting LPS, we review current studies concerning LPS-specific binders. Finally, we give perspectives for LPS research and the use of LPS-binding molecules.

Translatable Drug-Loaded Iron Oxide Nanophore Sensitizes Murine Melanoma Tumors to Monoclonal Antibody Immunotherapy

Macrophages comprise a significant portion of the immune cell compartment within tumors and are known contributors to tumor pathology; however, cancer immunotherapies targeting these cells are not clinically available. The iron oxide nanoparticle, ferumoxytol (FH), may be utilized as a nanophore for drug delivery to tumor-associated macrophages. We have demonstrated that a vaccine adjuvant, monophosphoryl lipid A (MPLA), can be stably captured within the carbohydrate shell of ferumoxytol without chemical modification of either the drug or the nanophore. This drug-nanoparticle combination (FH-MPLA) activated macrophages to an antitumorigenic phenotype at clinically relevant concentrations. In the immunotherapy-resistant B16-F10 model of murine melanoma, FH-MPLA treatment induced tumor necrosis and regression in combination with agonistic α-CD40 monoclonal antibody therapy. FH-MPLA, composed of clinically approved nanoparticle and drug payload, represents a potential cancer immunotherapy with translational relevance. FH-MPLA may be useful as an adjunctive therapy to existing antibody-based cancer immunotherapies which target only lymphocytic cells, reshaping the tumor immune environment.

10-Residue MyD88-Peptide Adopts β-Sheet Structure, Self-Assembles, Binds to Lipopolysaccharides, and Rescues Mice from Endotoxin-Mediated Lung-Infection and Death

Naturally occurring cationic antimicrobial peptides (AMPs) mostly adopt α-helical structures in bacterial membrane mimetic environments. To explore the design of novel β-sheet AMPs, we identified two short cationic amphipathic β-strand segments from the crystal structure of the innate immune protein, MyD88. Interestingly, of these, the 10-residue arginine-valine-rich synthetic MyD88-segment, KRCRRMVVVV (M3), exhibited β-sheet structure when bound to the outer membrane Gram-negative bacterial component, LPS. Isothermal titration calorimetric data showed that M3 bound to LPS with high affinity, and the interaction was hydrophobic in nature. Supporting these observations, computational studies indicated strong interactions of multiple and consecutive valine residues of M3 with the acyl chain of LPS. Moreover, M3 adopted nanosheet and nanofibrillar structure in 25% acetonitrile/water and isopropanol, respectively. M3 showed substantial antibacterial activities against both Gram-positive and Gram-negative bacteria which it appreciably retained in the presence of human serum and physiological salts. M3 was non-hemolytic against human red blood cells and non-cytotoxic to 3T3 cells up to 200 μM and to mice in vivo at a dose of 40 mg/kg. Furthermore, M3 neutralized LPS-induced pro-inflammatory responses in THP-1 cells and rat bone marrow-derived macrophages. Consequently, M3 attenuated LPS-mediated lung inflammation in mice and rescued them (80% survival at 10 mg/kg dose) against a lethal dose of LPS. The results demonstrate the identification of a 10-mer LPS-interacting, β-sheet peptide from MyD88 with the ability to form nanostructures and in vivo activity against LPS challenge in mice. The identified M3-template provides scope for designing novel bioactive peptides with β-sheet structures and self-assembling properties.

Affinity-Guided Isolation and Identification of Procyanidin B2 from Mangosteen (Garcinia mangostana L.) Rinds and its In Vitro LPS Binding and Neutralization Activities

Garcinia mangostana L. (mangosteen) is a tropical fruit that has been used for medicinal purposes in Southeast Asia for centuries. With an interest in its applications to treat infection, we sought to investigate the bioactive constituents of mangosteen and identified the phenolic compound procyanidin B2 from the mangosteen pericarp by examining lipopolysaccharide (LPS) binding capacity. The LPS binding and neutralization activities of procyanidin B2 were determined by a combination of biophysical and in silico techniques. The affinity of procyanidin B2 to LPS was 1.61 × 10^-5 M. Procyanidin B2 significantly neutralized LPS and selectively inhibited the LPS-induced release of tumor necrosis factor (TNF)-α from RAW264.7 cells in a dose-dependent manner. Binding thermodynamics revealed favorable hydrogen bonding and hydrophobic interactions between procyanidin B2 and LPS. Molecular simulations suggested that hydrogen bonding and hydrophobic interactions were involved in the binding process. These findings have, for the first time, shed light on the anti-inflammatory properties of procyanidin B2 through LPS binding and neutralization and provided a promising lead for the development of antiendotoxin agents.

Anti-endotoxin properties of cationic host defence peptides and proteins

The innate immune system of mammals contains a series of peptides with overall positive charge and an amphipathic structure which have a variety of important properties in host defences. Although these are often termed cationic antimicrobial peptides, they have numerous roles in innate defences in all complex species of life and thus we prefer to refer to them as host defence peptides. These roles include: (i) an ability to kill micro-organisms directly, ranging from bacteria to viruses, fungi, parasites and helminths; (ii) an adjuvant activity in the adaptive response; and (iii) a multiplicity of roles in modulating innate immunity, including an apparent ability to stimulate protective innate immunity while suppressing harmful inflammatory/septic responses. This latter property may be one of the more important activities of these peptides in vivo. Innate immunity is thought to be triggered by the interaction of conserved bacterial components with particular receptors including Toll-like receptors (TLRs) on host cells. However, the initiation of the innate immune response through this route may trigger a pro-inflammatory cascade that is the principle cause of harmful conditions such as sepsis. Since we are exposed to potentially dangerous pathogens on a daily basis, the host response must contain certain checks and balances. We propose that host defence peptides have a role in feed-back modulation of inflammation under normal (low-pathogen exposure) conditions. This review surveys the available information regarding the antiendotoxic/anti-inflammatory properties of host defence peptides, and will address whether this potential might be exploited for therapeutic benefit in sepsis.

The effective components of Huanglian Jiedu Decoction against sepsis evaluated by a lipid A-based affinity biosensor

ETHNOPHARMACOLOGICAL RELEVANCE

Huanglian Jiedu Decoction (HJD), the classical recipe for relieving fever and toxicity, has been used for treating sepsis in China for sixteen years. However, the effective components of HJD have not been elucidated until now. Therefore, there is a need to elucidate the effective components of HJD against sepsis on animal models induced by endotoxin (LPS). The affinity force of the effective components of HJD with lipid A was evaluated by a biosensor.

MATERIALS AND METHODS

Lipid A is regarded as the bioactive center of LPS and is always used as a drug target. In order to obtain the effective components of HJD against sepsis, seven fractions from HJD were tested by a biosensor method for assessing the affinity for lipid A. After further separation, the components were isolated from high lipid A-binding fractions and their affinities to lipid A were assessed with the aid of a biosensor. Their activities were then assayed by an in vivo experiment administered through a tail vein injection. The levels of LPS, TNF-α, and IL-6 from the blood were found and pathology experiments were performed.

RESULTS

Three out of the seven fractions exhibited high lipid A-binding affinities. Berberine, baicalin and geniposide were obtained from the three high lipid A-binding fractions. The animal experiments indicated that the levels of LPS, TNF-α and IL-6 in the medicated treatment groups were much lower than that of the model group ((**)P<0.01). The medicated treatment groups exhibited stronger protective activities on varying organs in the animal model.

CONCLUSIONS

Berberine, baicalin and geniposide could neutralize LPS by binding with lipid A and then reduce the release of IL-6 and TNF-α induced by LPS. Furthermore, berberine, baicalin and geniposide exhibited protective activities on varying organs compared to the animal model established by the LPS-induced. These results validate that the components from HJD neutralized LPS and then depressed the release of IL-6 and TNF-α induced by LPS. This gives further evidence that HJD would be a suitable treatment for sepsis and protecting vital organs.

A novel role of kukoamine B: Inhibition of the inflammatory response in the livers of lipopolysaccharide-induced septic mice via its unique property of combining with lipopolysaccharide

Kukoamine B (KB), derived from the traditional Chinese herb cortex Lycii, exerts anti-inflammatory effects due to its potent affinity with lipopolysaccharide (LPS) and CpG DNA; however, little is known regarding whether the in vivo administration of KB can effectively inhibit inflammation in septic mice. The present study thus aimed to investigate the inhibitory effects of KB on the inflammatory response in the livers of LPS-induced septic mice. KB treatment in the LPS-induced septic mice significantly decreased the plasma level of LPS. In addition, KB protected against liver injury, as confirmed by improved histology and decreased aminotransferase levels in the serum. Further experiments revealed that KB attenuated liver myeloperoxidase activity and reduced the expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1. These effects were accompanied by decreases in the levels of tumor necrosis factor α and interleukin-1β in the liver tissue. In parallel, the activity of nuclear factor-κ-gene binding (NF-κB) in the livers of LPS-induced septic mice was markedly inhibited with KB treatment. In combination, these results demonstrate that KB inhibits inflammation in septic mice by reducing the concentrations of plasma LPS, decreasing leukocyte sequestration and interfering with NF-κB activation, and, therefore, suppressing the pro-adhesive phenotype of endothelial cells.

Therapeutic interventions in sepsis: current and anticipated pharmacological agents

Sepsis is a clinical syndrome characterized by a multisystem response to a pathogenic assault due to underlying infection that involves a combination of interconnected biochemical, cellular and organ-organ interactive networks. After the withdrawal of recombinant human-activated protein C (rAPC), researchers and physicians have continued to search for new therapeutic approaches and targets against sepsis, effective in both hypo- and hyperinflammatory states. Currently, statins are being evaluated as a viable option in clinical trials. Many agents that have shown favourable results in experimental sepsis are not clinically effective or have not been clinically evaluated. Apart from developing new therapeutic molecules, there is great scope for for developing a variety of drug delivery strategies, such as nanoparticulate carriers and phospholipid-based systems. These nanoparticulate carriers neutralize intracorporeal LPS as well as deliver therapeutic agents to targeted tissues and subcellular locations. Here, we review and critically discuss the present status and new experimental and clinical approaches for therapeutic intervention in sepsis.

Antimicrobial activity of peptides derived from olive flounder lipopolysaccharide binding protein/bactericidal permeability-increasing protein (LBP/BPI)

We describe the antimicrobial function of peptides derived from the C-terminus of the olive flounder LBP BPI precursor protein. The investigated peptides, namely, ofLBP1N, ofLBP2A, ofLBP4N, ofLBP5A, and ofLBP6A, formed α-helical structures, showing significant antimicrobial activity against several Gram-negative bacteria, Gram-positive bacteria, and the yeast Candida albicans, but very limited hemolytic activities. The biological activities of these five analogs were evaluated against biomembranes or artificial membranes for the development of candidate therapeutic agents. Gel retardation studies revealed that peptides bound to DNA and inhibited migration on an agarose gel. In addition, we demonstrated that ofLBP6A inhibited polymerase chain reaction. These results suggested that the ofLBP-derived peptide bactericidal mechanism may be related to the interaction with intracellular components such as DNA or polymerase.

Lipid A-based affinity biosensor for screening anti-sepsis components from herbs

LPS (lipopolysaccharide), an outer membrane component of Gram-negative bacteria, plays an important role in the pathogenesis of sepsis and lipid A is known to be essential for its toxicity. Therefore it could be an effective measure to prevent sepsis by neutralizing or destroying LPS. Numerous studies have indicated that many traditional Chinese medicines are natural antagonists of LPS in vitro and in vivo. The goal of this study is to develop a rapid method to screen anti-sepsis components from Chinese herbs by use of a direct lipid A-based affinity biosensor technology based on a resonant mirror. The detergent OG (n-octyl β-D-glucopyranoside) was immobilized on a planar non-derivatized cuvette which provided an alternative surface to bind the terminal hydrophilic group of lipid A. A total of 78 herbs were screened based on the affinity biosensor with a target of lipid A. The aqueous extract of PSA (Paeonia suffruticosa Andr) was found to possess the highest capability of binding lipid A. Therefore an aqueous extraction from this plant was investigated further by our affinity biosensor, polyamide chromatography and IEC–HPLC. Finally, we obtained a component (PSA-I-3) from Paeonia suffruticosa Andr that was evaluated with the affinity biosensor. We also studied the biological activities of PSA-I-3 against sepsis in vitro and in vivo to further confirm the component we screened with the biosensor. In vitro, we found that PSA-I-3 could decrease TNFα (tumour necrosis factor α) release from RAW264.7 cells induced by LPS in a dose-dependent manner. In vivo, it increased remarkably the survival of KM (KunMing) mice by challenging both lethal-dose LPS and heat-killed Escherichia coli compared with control groups. Our results suggest that the constructed affinity biosensor can successfully screen the anti-sepsis component from Chinese herbs.

Transcription networks responsible for early regulation of Salmonella-induced inflammation in the jejunum of pigs

Background

The aim of this study was to identify transcription factors/regulators that play a crucial role in steering the (innate) immune response shortly (within a few hours) after the first contact of the intestinal mucosa with an inflammatory mediator, and to test whether the processes regulated by these factors/regulators can be modulated by chemical substances of natural origin.

Methods

We experimentally induced inflammation by perfusion of surgically applied jejunal loops with Salmonella enterica subspecies enterica serovar Typhimurium DT104 in three pigs. Segments of mock and Salmonella treated loops were dissected after 2, 4 and 8 hours of perfusion. IL8 and IL1-beta mRNA expression levels were measured in mucosal scrapings of all segments. Furthermore, intra-animal microarray comparisons (isogenic) between Salmonella and mock treated segments after 8 hours, and inter-animal comparisons between similar Salmonella-treated loops of each pig at 2 and 4 hours, were performed.

Results

IL-1beta and IL8 mRNA levels, and intra-animal microarray comparisons at 8 hours between Salmonella and mock treated segments showed that the response-time and type of response to Salmonella was different in all three pigs. This plasticity allowed us to extract a comprehensive set of differentially expressed genes from inter-animal comparisons at 2 and 4 hours. Pathway analysis indicated that many of these genes play a role in induction and/or tempering the inflammatory response in the intestine. Among them a set of transcription factors/regulators known to be involved in regulation of inflammation, but also factors/regulators for which involvement was not expected. Nine out of twenty compounds of natural origin, which according to literature had the potential to modulate the activity of these factors/regulators, were able to stimulate or inhibit a Salmonella-induced mRNA response of inflammatory-reporter genes IL8 and/or nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha in cultured intestinal porcine epithelial cells.

Conclusions

We describe a set of transcription factors/regulators possibly involved in regulation of “very early” immune mechanism which determines the inflammatory status of the intestine later on. In addition, we show that these mechanisms may be modulated by chemical substances of natural origin.

Forsythoside B protects against experimental sepsis by modulating inflammatory factors

The present study investigated the effects of Forsythoside B on an experimental model of sepsis induced by caecal ligation and puncture (CLP) in rats and elucidated the potential mechanism in cultured RAW 264.7 cells. Results showed that Forsythoside B concentration-dependently down-regulated the levels of TNF-α, IL-6 and high-mobility group-box 1 protein (HMGB1) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, inhibited the IκB kinase (IKK) pathway and modulated nuclear factor (NF)- κB. Intravenous injection (i.v.) of Forsythoside B alone or plus Imipenem reduced serum levels of TNF-α, IL-6, HMGB1, triggering receptor expressed on myeloid cells (TREM-1) and endotoxin, while the serum level of IL-10 was up-regulated and myeloperoxidase (MPO) in lung, liver and small intestine was reduced. Meanwhile, i.v. of Forsythoside B alone or plus Imipenem reduced CLP-induced lethality in rats. These data indicated that the antisepsis effect of Forsythoside B is mediated by decreasing local and systemic levels of a wide spectrum of inflammatory mediators. Its antisepsis mechanism may be that Forsythoside B binds to LPS and reduces the biological activity of serum LPS, and inhibits NF-κB activition. Our studies enhance the case for the use of Forsythoside B in sepsis. Forsythoside B itself has promise as a therapy for the treatment of sepsis in humans.

Kukoamine B, a novel dual inhibitor of LPS and CpG DNA, is a potential candidate for sepsis treatment

BACKGROUND AND PURPOSE

Lipopolysaccharides (LPS) and oligodeoxynucleotides containing CpG motifs (CpG DNA) are important pathogenic molecules for the induction of sepsis, and thus are drug targets for sepsis treatment. The present drugs for treating sepsis act only against either LPS or CpG DNA. Hence, they are not particularly efficient at combating sepsis as the latter two molecules usually cooperate during sepsis. In this study, a natural alkaloid compound kukoamine B (KB) is presented as a potent dual inhibitor for both LPS and CpG DNA.

EXPERIMENTAL APPROACH

The affinities of KB for LPS and CpG DNA were assessed using biosensor technology. Direct interaction of KB with LPS and CpG DNA were evaluated using neutralization assays. Selective inhibitory activities of KB on pro-inflammatory signal transduction and cytokine expression induced by LPS and CpG DNA were analysed by cellular assays. Protective effects of KB in a sepsis model in mice were elucidated by determining survival and circulatory LPS and tumour necrosis factor-alpha (TNF-α) concentrations.

KEY RESULTS

KB had high affinities for LPS and CpG DNA. It neutralized LPS and CpG DNA and prevented them from interacting with mouse macrophages. KB selectively inhibited LPS- and CpG DNA-induced signal transduction and expression of pro-inflammatory mediators without interfering with signal pathways or cell viability in macrophages. KB protected mice challenged with heat-killed Escherichia coli, and reduced the circulatory levels of LPS and TNF-α.

CONCLUSIONS AND IMPLICATIONS

This is the first report of a novel dual inhibitor of LPS and CpG DNA. KB is worthy of further investigation as a potential candidate to treat sepsis.

Protective effects of antimicrobial peptide S-thanatin against endotoxic shock in mice introduced by LPS

Sepsis continues to be a major unresolved medical challenge of the present. Severe sepsis and septic shock are the leading causes of multiple organ failure and mortality in noncoronary intensive care units (ICUs). The primary reason of septic shock is the activation of host effecter cells by endotoxin and lipopolysaccharide (LPS) associated with cell membranes of gram-negative bacteria. For these reasons, the key point of treatment is removing LPS. S-thanatin (Ts), an analog of thanatin, was synthesized by substituting the 15th amino acid of threonine with serine, which showed a broad antimicrobial activity against gram-negative and gram-positive bacteria. We have reported its LPS-binding and -neutralizing activity in vitro. The aim of this study is to examine the LPS-neutralizing activities and the protective effects of S-thanatin in vivo. Every mice was injected intraperitoneally with LPS (from Escherichia coli O111:B4) 150μg before injected intraperitoneally or vena caudalis with 3mg/kg, 6mg/kg and 12mg/kg, and measured endotoxin and tumor necrosis factor alpha (TNF-α) concentrations in plasma, as well as lethality. The results showed that S-thanatin can significantly reduce endotoxin and TNF-α level in plasma, at the same time resulting in the highest survival rates.

Lipopolysaccharide (LPS) detoxification of analogue peptides derived from limulus anti-LPS factor

Lipopolysaccharide (LPS) plays a critical role in the pathogenesis of sepsis due to gram-negative bacterial infections. Therefore, LPS-neutralizing molecules could have important clinical applications. Our previous work showed, CLP19, an analogue peptide derived from limulus anti-LPS factor (LALF), possessed the capacity to neutralize LPS and thereby inhibit the LPS-induced responses. However, potential cytotoxicity of CLP19 was also found, especially when added to human red blood cells. Accordingly we further developed two peptides (designated as CLP19-1 and CLP19-2) by single- and double-point amino acid substitution of CLP19, respectively, in order to reduce its toxicity and meanwhile retain the anti-LPS activity. In this study, the LPS-detoxifying effectiveness of these peptides was evaluated both in vitro and in vivo. CLP19-1 was found to dose-dependently neutralize LPS in vitro, with significantly lower hemolysis of red blood cells as compared with CLP19. Further in vivo tests verified that CLP19-1 exerted significant protective effects on mice against LPS, characterized by significantly improved survival, decreasing of tumor necrosis factor alpha (TNF-α) serum level and alleviation of tissue injury. Our work indicates that CLP19-1 is worthy of further study as potential anti-LPS agents for the management of sepsis.

Interaction of antimicrobial peptide s-thanatin with lipopolysaccharide in vitro and in an experimental mouse model of septic shock caused by a multidrug-resistant clinical isolate of Escherichia coli

s-thanatin, an analogue of thanatin, was synthesised by substituting the fifteenth amino acid threonine with serine and showed broad antimicrobial activity against Gram-negative and Gram-positive bacteria. To evaluate its antimicrobial activity against a multidrug-resistant (MDR) clinical isolate as well as its anti-endotoxin activity, its lipopolysaccharide (LPS)-binding and -neutralising activity in vitro and its therapeutic efficacy in an experimental model of septic shock caused by a MDR clinical isolate of Escherichia coli were studied. The ability of s-thanatin to bind or neutralise LPS from E. coli O111:B4 was determined using a quantitative assay kit. Male ICR mice were given an intraperitoneal (i.p.) administration of 2x10(10) colony-forming units of E. coli E79466. Following bacterial challenge, all animals were randomised to receive i.p. administration of saline, 40mg/kg ceftazidime (CAZ), or 40mg/kg CAZ+s-thanatin (10, 20 or 40mg/kg). The results showed that s-thanatin not only completely bound to the LPS (median effective concentration of 17.5microg/mL) but also improved the survival and reduced the number of inoculated bacteria in a mouse model of septic shock. s-thanatin may be an attractive candidate to develop as an anti-MDR bacterial agent.

Extraction of the anti-sepsis component from Terminaliachebula Retz and evaluation of its biological activities

Many clinical experiments and studies have demonstrated that traditional Chinese medicines possess the capacity for being used in anti-sepsis. In this paper, we screened 78 herbs based on biosensor technology by targeting of lipid A. Terminaliachebula Retz was found to possess the highest capability of binding lipid A. With CER (cation-exchange resin) and HPLC, we obtained three active components extracted from Terminaliachebula Retz, and named them TCR1, TCR2 and TCR3 respectively. These three components were evaluated with the biosensor, and it was found that the TCR3 was the most capable candidate to bind lipid A. We also studied the biological activities of TCR3 against sepsis in vitro and in vivo. in vitro, TCR3 could significantly inhibit LPS (lipopolysaccharide)-induced LAL (Limulus amoebocyte lysate)) from agglutination and decrease TNFalpha (tumour necrosis factor alpha) release from RAW264.7 cells induced by LPS in a dose-dependent manner. in vivo, TCR3 could significantly protect mice against a lethal challenge with LPS and heat-killed Escherichia coli 35218 in a dose-dependent manner. These results demonstrate that Terminaliachebula Retz is an important herb to neutralize LPS and it has the potential to serve as a treatment for sepsis.

Bacterial endotoxin stimulates adipose lipolysis via toll-like receptor 4 and extracellular signal-regulated kinase pathway

Bacterial endotoxin/lipopolysaccharide elicits inflammatory responses and also elevates circulating levels of free fatty acids (FFAs) and impairs insulin sensitivity. Serum FFA elevation in acute endotoxemia has long been thought to be due to endotoxin dysregulating lipid disposal and counterregulatory hormones and cytokines. Here, we investigated the direct lipolysis effect of endotoxin in rodents and in isolated primary adipocytes. Endotoxin increases lipolysis in vivo in adipose tissues, elevates circulating FFA level, induces insulin resistance in rats, and directly stimulates chronic lipolysis in vitro in adipocytes. The lipolytic action of endotoxin is mediated via its lipid A moiety and is blocked by anti-endotoxin peptides. Neither adipocytokine secretion nor nuclear factor-kappaB activation is involved in endotoxin-induced lipolysis. Different from catecholamine, endotoxin stimulates lipolysis without elevating cAMP production and activating protein kinase A and protein kinase C. Instead, endotoxin induces phosphorylation of Raf-1, MEK1/2, and ERK1/2. Upon inhibition of ERK1/2 but not JNK and p38 MAPK, endotoxin-stimulated lipolysis ceases. Endotoxin causes perilipin down-regulation and phosphorylation and increases the activity and protein levels of hormone-sensitive lipase and adipose triglyceride lipase but does not induce hormone-sensitive lipase translocation to intracellular lipid droplets. In TLR4 (Toll-like receptor 4)-deficient mice and adipocytes, endotoxin fails to increase in vivo and in vitro lipolysis. These findings suggest that endotoxin stimulates lipolysis via TLR4 and ERK1/2 signaling in adipocytes. The lipolytic action of endotoxin liberates FFA efflux from adipocytes to the bloodstream, which is a possible basis for systemic FFA elevation and insulin resistance in endotoxemia or Gram-negative bacterial infection.

Lipid A-induced responses in vivo

The lipid A analogs used in preclinical studies and clinical trials are not naturally-occurring forms of lipid A; they are synthetic molecules produced to be less toxic than lipid A itself and they do not reproduce the effects of natural lipid A molecules especially in vivo. The responses induced by lipid A analogs are summarized in this chapter: their fate in the blood stream and their toxicity as well as the lipid A tolerance and the tumor immune responses they induce. Lipid A is not found in the mammalian organism under normal circumstances so its use in cancer therapy raises important questions as to its different effects in vivo and its toxicity, particularly in cancer patients. Lipid A has to be injected intravenously (i.v.) to study its effects. Injections of chemically synthesized lipid A in humans and in animals produce sepsis symptoms, such as tachycardia, tachypnea, hyper or hypothermia and leukocytosis or leukopenia. Similar manifestations are observed after injection of purified lipopolysaccharide (LPS), which is why lipid A is usually thought of as the active part of LPS. While lipid A injection is therefore expected to induce reactions similar to septic shock, the lipid A molecules used to treat cancer are not natural forms but analogs, produced by chemical synthesis or genetic engineering, specifically selected for their low toxicity. The in vivo effects of such low-toxicity lipid A analogs are summarized in this chapter.

Role of host defense peptides of the innate immune response in sepsis

Innate immune response and its effector molecules have received growing attention in research. Host defense peptides are known to be antimicrobially active. Recently, the peptides have been recognized as potent signaling molecules for cellular effectors of both innate and adaptive immunity. Mammalian peptides in particular revealed immunomodulatory functions, including endotoxin-binding and -neutralizing capacity, chemotactic activities, induction of cytokines and chemokines, promotion of wound healing, and angiogenesis. In sepsis, they present a family of natural substances that can be used in combination with antibiotics to complete a broad-spectrum antimicrobial regimen with endotoxin-neutralizing properties. Although there are side effects, host defense peptides have the potential to be significant reinforcements to the currently available therapeutic options in the future. In this review, we analyze the role of host defense peptides in infection and immune response, and discuss recent efforts to establish host defense peptides as potent novel therapeutic agents for the treatment of sepsis.

An anti-sepsis monomer, 2',5,6',7-tetrahydroxyflavanonol (THF), identified from Scutellaria baicalensis Georgi neutralizes lipopolysaccharide in vitro and in vivo

Lipopolysaccharide (LPS) is a known trigger in the pathogenesis of sepsis, lipid A being the toxic component. One of several adjuvant therapeutic approaches for severe sepsis is currently focusing on the neutralization of LPS. In order to obtain the components from traditional Chinese herbs that can neutralize the endotoxin, aqueous extractions of twelve herbs were tested using affinity biosensor technology. From twelve herbs, Scutellaria baicalensis Georgi (Huang Qin) found to possess high lipid A-binding abilities, and was selected in subsequent experiments. After subjected to macroporous adsorptive resins and HPLC, we obtained 2',5,6',7-tetrahydroxyflavanonol (THF) from S. baicalensis Georgi under the direction of neutralization of LPS and reducing proinflammatory cytokines. In vitro, THF directly bound to LPS and neutralized its activity. THF not only down-regulated TNF-alpha mRNA expression but also decreased TNF-alpha and IL-6 release from RAW264.7 cells induced by LPS in a dose-dependent manner. THF-mediated inhibition on proinflammatory cytokine release is probably associated with downregulation of LPS-induced TLR4 mRNA augmentation. In vivo, THF could significantly protect mice against a lethal challenge with heat-killed E. coli 35218 (E. coli 35218) in a dose-dependent manner, and decreased the plasma LPS level in endotoxemia mice. These findings provide compelling evidence that THF may be an important potential drug for sepsis treatment. Considering the inhibitory effects of THF on LPS-induced cytokine release are unlikely due to its nonspecific cellular toxicity, THF should be considered as a safe putative candidate for development as a drug for sepsis treatment.

Effect of plasma phospholipid transfer protein deficiency on lethal endotoxemia in mice

Lipopolysaccharides (LPS) are components of Gram-negative bacteria. The cellular response from the host to LPS is mediated through stepwise interactions involving the lipopolysaccharide-binding protein (LBP), CD14, and MD-2, which produces the rearrangement of TLR4. In addition to LBP, the lipid transfer/lipopolysaccharide-binding protein gene family includes the phospholipid transfer protein (PLTP). Here we show that the intravascular redistribution of LPS from the plasma lipoprotein-free fraction toward circulating lipoproteins is delayed in PLTP-deficient mice. In agreement with earlier in vitro studies, which predicted the neutralization of the endotoxic properties of LPS when associated with lipoproteins, significant increases in the plasma concentration of proinflammatory cytokines were found in PLTP-deficient as compared with wild type mice. Similar inflammatory damage occurred in tissues from wild type and PLTP-deficient mice 24 h after one single intraperitoneal injection of LPS but with a more severe accumulation of red blood cells in glomeruli of LPS-injected PLTP-deficient mice. Complementary ex vivo experiments on isolated splenocytes from wild type and PLTP-deficient mice further supported the ability of cell-derived PLTP to prevent LPS-mediated inflammation and cytotoxicity when combined with lipoprotein acceptors. Finally, PLTP deficiency in mice led to a significant increase in LPS-induced mortality. It is concluded that increasing circulating levels of PLTP may constitute a new and promising strategy in preventing endotoxic shock.

A synthetic cyclic peptide derived from Limulus anti-lipopolysaccharide factor neutralizes endotoxin in vitro and in vivo

Endotoxin, also known as lipopolysaccharide (LPS), is the major mediator of septic shock due to Gram-negative bacterial infections. Recently, much attention has been focused on cationic peptides which possess the potential to detoxify LPS. Limulus anti-LPS factor (LALF), a protein found in the horseshoe crab (Limulus polyphemus), has been proved with striking anti-LPS effects. We synthesized a cyclic peptide (CLP-19), and then investigated its bioactivity both in vitro and in vivo. The ability of CLP-19 to neutralize LPS in vitro was tested using a Limulus amebocyte lysate (LAL) assay and the LPS-binding affinity was measured with an affinity biosensor method. The synthetic peptide LALF31-52 (residues 31 to 52 of LALF) was used as the positive control peptide in this study. It was found that CLP-19 exhibited the significant activity to antagonize LPS without observable cytotoxicity effect on mouse macrophages. CLP-19 directly bound to LPS, and neutralized it in a dose-dependent manner in the LAL assay. Moreover, CLP-19 also showed the remarkable ability to protect mice from lethal LPS attack and to inhibit the LPS-induced tumor necrosis factor alpha (TNF-alpha) release by decreasing serum LPS in vivo. Our work suggests that this peptide is worthy of further investigation as a potential anti-LPS agent in the treatment of septic shock.

Antimalarial artesunate protects sepsis model mice against heat-killed Escherichia coli challenge by decreasing TLR4, TLR9 mRNA expressions and transcription factor NF-kappa B activation

Bacterial DNA (bDNA) and lipopolysaccharide (LPS) are potent activators of immune cells such as monocytes and macrophages, which contribute to systemic inflammatory response syndrome (SIRS) and sepsis. Unfortunately, many experimental inflammatory antagonist-based therapies have failed in sepsis trials, and currently there is only one adjuvant therapy in clinical use, e.g. activated protein C. Artesunate (AS), a water-soluble derivative of dihydroartemisinin, has recently been demonstrated to protect against LPS-induced human umbilical vein endothelial cell (HUVEC) activation and injury by inhibiting tumor necrosis factor-alpha (TNF-alpha) mRNA expression. In the present study, heat-killed Escherichia coli was used to induce sepsis in the animal models. We observed that AS could protect mice against a lethal challenge with heat-killed E. coli in a dose-dependent manner. This protection was associated with reductions in serum TNF-alpha and measurable endotoxin levels. In addition, the treatment of murine peritoneal macrophage cells with AS strongly inhibited the release of TNF-alpha and IL-6 induced by CpG oligodeoxynucleotide (CpG ODN), LPS, or heat-killed E. coli in a dose-dependent manner. Experiments using affinity sensor technology revealed that AS could not directly bind to CpG ODN or LPS. Moreover, AS could not neutralize LPS in vitro. Further, flow cytometry revealed that AS could not alter the binding of CpG ODN to cell surfaces but could promote CpG ODN accumulation within RAW264.7 cells. Furthermore, AS reduced the expressions of TLR4 and TLR9 mRNA that were stimulated by LPS, CpG ODN, or heat-killed E. coli and inhibited heat killed E. coli-induced NF-kappaB activation. In conclusion, our results demonstrated that AS-mediated protection against a lethal heat-killed E. coli challenge was associated with a reduction in proinflammatory cytokine release and endotoxin levels via a mechanism involving a decrease in TLR4, TLR9 mRNA expression and NF-kappaB activation.

Endotoxin downregulates peroxisome proliferator-activated receptor-gamma via the increase in TNF-alpha release

The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is anti-inflammatory in a cell-based system and in animal models of endotoxemia. We have shown that PPAR-gamma gene expression is downregulated in macrophages after lipopolysaccharide (LPS) stimulation. However, it remains unknown whether hepatic PPAR-gamma is altered in sepsis and, if so, whether LPS directly downregulates PPAR-gamma. To study this, rats were subjected to sepsis by cecal ligation and puncture (CLP). Hepatic tissues were harvested at 5, 10, and 20 h after CLP. PPAR-gamma gene expression and protein levels were determined by RT-PCR and Western blot analysis, respectively. The results showed that PPAR-gamma gene expression decreased at 10 and 20 h and that its proteins levels were reduced at 20 h after CLP. PPAR-gamma levels were also decreased in animals that were administered LPS. To determine the direct effects of LPS on PPAR-gamma downregulation, LPS binding agent polymyxin B (PMB) was administered intramuscularly after CLP. The administration of PMB significantly reduced plasma levels of endotoxin, but it did not prevent the downregulation of PPAR-gamma expression. We found that circulating levels of TNF-alpha still remained significantly elevated in PMB-treated septic animals. We, therefore, hypothesize that the decrease of PPAR-gamma expression is TNF-alpha dependent. To investigate this, Kupffer cells (KCs) were isolated from normal rats and stimulated with LPS or TNF-alpha. TNF-alpha significantly attenuated PPAR-gamma gene expression in KCs. Although LPS decreased PPAR-gamma in KCs, the downregulatory effect of LPS was blocked by the addition of TNF-alpha-neutralizing antibodies. Furthermore, the administration of TNF-alpha-neutralizing antibodies to animals before the onset of sepsis prevented the downregulation of PPAR-gamma in sepsis. We, therefore, conclude that LPS downregulates PPAR-gamma expression during sepsis via an increase in TNF-alpha release.

A peptide derived from human bactericidal/permeability-increasing protein (BPI) exerts bactericidal activity against Gram-negative bacterial isolates obtained from clinical cases of bovine mastitis

Gram-negative bacteria are responsible for approximately one-third of the clinical cases of bovine mastitis and can elicit a life-threatening, systemic inflammatory response. Lipopolysaccharide (LPS) is a membrane component of Gram-negative bacteria and is largely responsible for evoking the inflammatory response. Antibiotic and anti-inflammatory therapy for treating Gram-negative infections remains suboptimal. Bactericidal/permeability-increasing protein (BPI) is a neutrophil-derived protein with antimicrobial and LPS-neutralizing properties. Select peptide derivatives of BPI are reported to retain these properties. The objective of this study was to evaluate the antimicrobial activity of a human BPI-derived synthetic peptide against clinical bovine mastitis isolates of Gram-negative bacteria. A hybrid peptide was synthesized corresponding to two regions of human BPI (amino acids 90-99 and 148-161), the former of which has bactericidal activity and the latter of which has LPS-neutralizing activity. The minimum inhibitory (MIC) and bactericidal (MBC) concentrations of this peptide against various genera of bacteria were determined using a broth microdilution assay. The MIC's were determined to be: 16-64 microg/ml against Escherichia coli; 32-128 microg/ml against Klebsiella pneumoniae and Enterobacter spp.; and 64-256 microg/ml against Pseudomonas aeruginosa. The MBC's were equivalent to or 1-fold greater than corresponding MIC's. The peptide had no growth inhibitory effect on Serratia marcescens. The antimicrobial activity of the peptide was retained in the presence of serum, but severely impaired in milk. Further functional evaluation of the peptide demonstrated its ability to completely neutralize LPS. Together, these data support additional investigations into the therapeutic application of BPI to the treatment of Gram-negative infections in cattle.

ROLE OF BACTERIAL ENDOTOXIN IN CHRONIC HEART FAILURE

Proinflammatory cytokines are now thought to play a key role in the pathophysiology of chronic heart failure, driving both symptomatic presentation and disease progression. We propose that this proinflammatory state, in turn, may be sustained through a chronic release of enterically derived bacterial endotoxin. Human trials have indicated that bacterial decontamination of the gut with concomitant decrease in lipopolysaccharide (LPS) has a positive outcome on heart disease patients. Antiendotoxin antibodies may thus represent therapeutic agents in this setting. Previously, antiendotoxin antibodies were targeted to the inner hydrophobic lipid A moiety of endotoxin in an attempt to neutralize its toxicity. These antibodies failed because they lacked specificity and bound to LPS weakly. In contrast, our studies on antiendotoxin antibodies have revealed that antibodies targeted to the hydrophilic oligosaccharides of the endotoxin have the potential to bind specifically with high affinity. Development of immunotherapeutics that can reduce systemic LPS or other agents, such as bactericidal/permeability-increasing protein that can neutralize LPS and limit inflammation safely, will enable the role of LPS in chronic heart failure to be elucidated and may pave the way to develop a new generation of effective therapeutic agents that may be directed to the treatment of chronic heart failure.

Lipopolysaccharide-binding and neutralizing activities of surfactin C in experimental models of septic shock

To evaluate the anti-endotoxin activity of surfactin C, we studied its lipopolysaccharide-binding activity in vitro and therapeutic efficacy in experimental models of gram-negative septic shock. The ability of surfactin C to bind LPS from Escherichia coli O111:B4 was determined using a limulus chromogenic assay. Male ICR mice and Sprague-Dawley rats were given intraperitoneal administration of 1x10(9) colony forming units of E. coli ATCC 25922. After bacterial challenge, all animals were randomized to receive intraperitoneally saline, polymyxin B or surfactin C. Surfactin C not only completely bound to the LPS (its median effective concentration being 13.75 microM) but also improved the survival and reduced of the number of inoculated bacteria in the mouse model of septic shock. Surfactin C reduced the plasma endotoxin, tumor necrosis factor-alpha and nitric oxide levels in response to septic shock in rats.

The antimalarial artemisinin synergizes with antibiotics to protect against lethal live Escherichia coli challenge by decreasing proinflammatory cytokine release

In the present study artemisinin (ART) was found to have potent anti-inflammatory effects in animal models of sepsis induced by CpG-containing oligodeoxy-nucleotides (CpG ODN), lipopolysaccharide (LPS), heat-killed Escherichia coli 35218 or live E. coli. Furthermore, we found that ART protected mice from a lethal challenge by CpG ODN, LPS, or heat-killed E. coli in a dose-dependent manner and that the protection was related to a reduction in serum tumor necrosis factor alpha (TNF-alpha). More significantly, the administration of ART together with ampicillin or unasyn (a complex of ampicillin and sulbactam) decreased mortality from 100 to 66.7% or 33.3%, respectively, in mice subjected to a lethal live E. coli challenge. Together with the observation that ART alone does not inhibit bacterial growth, this result suggests that ART protection is achieved as a result of its anti-inflammatory activity rather than an antimicrobial effect. In RAW264.7 cells, pretreatment with ART potently inhibited TNF-alpha and interleukin-6 release induced by CpG ODN, LPS, or heat-killed E. coli in a dose- and time-dependent manner. Experiments utilizing affinity sensor technology revealed no direct binding of ART with CpG ODN or LPS. Flow cytometry further showed that ART did not alter binding of CpG ODN to cell surfaces or the internalization of CpG ODN. In addition, upregulated levels of TLR9 and TLR4 mRNA were not attenuated by ART treatment. ART treatment did, however, block the NF-kappaB activation induced by CpG ODN, LPS, or heat-killed E. coli. These findings provide compelling evidence that ART may be an important potential drug for sepsis treatment.

Protective effects of antimicrobial peptides derived from the beetle Allomyrina dichotoma defensin on endotoxic shock in mice

Synthetic peptides, Arg-Leu-Tyr-Leu-Arg-Ile-Gly-Arg-Arg-NH2 (peptide A) and Arg-Leu-Arg-Leu-Arg-Ile-Gly-Arg-Arg-NH2 (peptide B), derived from the beetle Allomyrina dichotoma defensin, have not only antimicrobial activities but also anti-inflammatory effects by inhibiting tumour necrosis factor-alpha(TNF-alpha) production. In the present study, we evaluated the lipopolysaccharide (LPS)-binding activities and the protective effects of these peptides on LPS-induced lethal shock in d-galactosamine (GalN)-sensitized mice. These peptides were shown to bind to erythrocytes coated with LPS and the binding activity of peptide A to LPS was significantly higher than those of peptide B and polymyxin B. Mice were injected intraperitoneally with peptide A or B at doses of 25, 50, 100 and 150 mg/kg before an injection of Salmonella abortusequi LPS (5 microg/kg) and GalN (1 g/kg) (LPS+GalN). All of wild-type mice died within 24 h after challenged with LPS+GalN. All of TNF-alpha-deficient mice challenged with LPS+GalN survived. An injection of peptide A immediately after challenge with LPS+GalN resulted in significantly improved survival rates in a dose dependent manner. Peptide B showed only minor protection. The levels of TNF-alpha in the ameliorated mice by peptide A were significantly lower than those of challenge control, suggesting a suppressive effect of peptide A on TNF-alpha production. Furthermore, peptide A-treated mice showed significantly lower levels of asparate aminotransferase and alanine aminotransferase when compared to challenge control. Concordantly, hemorrhage and necrosis in the liver of peptide A-treated mice were less apparent than those of untreated control mice. These results suggest that peptide A has a protective effect on LPS-induced mortality in this mouse model.

Inflammation--a new therapeutic target in pneumonia

Inflammation is a hallmark of pneumonia. Therefore, managing inflammation is an attractive adjunct to targeted antibiotic therapy, mainly in severe pneumonia. Recent investigations indicate that glucocorticoids given in physiological doses (from 10-fold to 100-fold less than doses administered in the past) could be of benefit. We could also manage inflammation by administering or influencing cytokines. A major concern is that drugs designed to target a single cytokine or receptor could prove ineffective due to the redundancy of signaling pathways involved. This may require selection of drugs with broad activity or the targeting of molecules common to inflammatory signaling pathways. Drugs affecting multiple molecules or key inflammatory pathway intermediates could be more effective, but their use will need to be weighed against the risk of impairing innate immunity. Indirect approaches to manage inflammation, such as neutralizing cytotoxic substances in the lung (e.g., inhibiting, neutralizing and eliminating endotoxin), could be used in combination with other approaches. Ideally, potential treatment of life-threatening bacterial pneumonia will combine immunoadjuvant and conventional antibiotic therapy, although intense clinical research with immunotherapy has not yet yielded a successful treatment adjunct. We believe that compounds capable of stimulating early host defense and microbial clearance, but not the later phases of inflammatory tissue injury associated with sepsis, may be advantageous.

Polymyxin B: an ode to an old antidote for endotoxic shock

Endotoxic shock, a syndrome characterized by deranged hemodynamics, coagulation abnormalities, and multiple system organ failure is caused by the release into the circulation of lipopolysaccharide (LPS), the structurally diverse component of Gram-negative bacterial outer membranes, and is responsible for 60% mortality in humans. Polymyxin B (PMB), a cyclic, cationic peptide antibiotic, neutralizes endotoxin but induces severe side effects in the process. The potent endotoxin neutralizing ability of PMB, however, offers possibilities for designing non-toxic therapeutic agents for combating endotoxicosis. Amongst the numerous approaches for combating endotoxic shock, peptide mediated neutralization of LPS seems to be the most attractive one. The precise mode of binding of PMB to LPS and the structural features involved therein have been elucidated only recently using a variety of biophysical approaches. These suggest that efficient neutralization of endotoxin by PMB is not achieved by mere binding to LPS but requires its sequestration from the membrane. Incorporation of this feature into the design of endotoxin neutralizing peptides should lead to the development of effective antidotes for endotoxic shock.

Survey of the year 2004 commercial optical biosensor literature

The year 2004 represents a milestone for the biosensor research community: in this year, over 1000 articles were published describing experiments performed using commercially available systems. The 1038 papers we found represent an approximately 10% increase over the past year and demonstrate that the implementation of biosensors continues to expand at a healthy pace. We evaluated the data presented in each paper and compiled a 'top 10' list. These 10 articles, which we recommend every biosensor user reads, describe well-performed kinetic, equilibrium and qualitative/screening studies, provide comparisons between binding parameters obtained from different biosensor users, as well as from biosensor- and solution-based interaction analyses, and summarize the cutting-edge applications of the technology. We also re-iterate some of the experimental pitfalls that lead to sub-optimal data and over-interpreted results. We are hopeful that the biosensor community, by applying the hints we outline, will obtain data on a par with that presented in the 10 spotlighted articles. This will ensure that the scientific community at large can be confident in the data we report from optical biosensors.