Enhancement of nonspecific immunity to Klebsiella pneumoniae infection by a synthetic immunoadjuvant (N-acetylmuramyl-L-alanyl-D-isoglutamine) and several analogs

N-Acetylmuramyl-L-alanyl-D-isoglutamine and four other synthetic adjuvants that are structural analogs of part of the mycobacterial peptidoglycan monomer are shown to enhance the nonspecific immunity of mice infected by Klebsiella pneumoniae. These compounds are active by various routes, including oral administration; they are also effective when administered after challenge. Of the seventeen other analogs tested, none is able to increase significantly resistance to infection, although seven of these molecules are adjuvant-active in saline. Previous results have shown that in contrast to lipopolysaccharides, these synthetic adjuvants are devoid of immunogenicity, mitogenicity, and toxicity in normal or adrenalectomized mice.

Peptidoglycan and lipoteichoic acid from Staphylococcus aureus induce tumor necrosis factor alpha, interleukin 6 (IL-6), and IL-10 production in both T cells and monocytes in a human whole blood model

We have examined the ability of peptidoglycan (PepG) and lipoteichoic acid (LTA) isolated from Staphylococcus aureus to induce the release of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and IL-10 in whole human blood and identified the cellular origins of these cytokines. Both PepG and LTA induced transient increases in TNF-alpha and IL-10 in plasma, with peak values at 6 and 12 h, respectively. IL-6 values increased throughout the experimental period (24 h). The TNF-alpha, IL-6, and IL-10 release induced by PepG and LTA was dose dependent. Only PepG was a potent inducer of TNF-alpha secretion. After stimulation of whole blood with PepG or LTA, very pure populations of monocytes (CD14 positive), T cells (CD2 positive), B cells (CD19 positive), and granulocytes (CD15 positive) were isolated by immunomagnetic separation and analyzed by reverse transcription-PCR for mRNA transcripts encoding TNF-alpha, IL-6, and IL-10. The TNF-alpha mRNA results were inconclusive. In contrast, PepG induced IL-6 and IL-10 mRNA accumulation in both T cells and monocytes. LTA, as well as lipopolysaccharide, induced IL-6 and IL-10 mRNA production in monocytes and possibly in T cells. Whether granulocytes and B cells produce cytokines in response to bacterial stimuli remains obscure. Blockade of the CD14 receptors with monoclonal antibodies (18D11) had no influence on the PepG-induced release of TNF-alpha but attenuated the LTA-induced release of the same cytokine. In conclusion, our data indicate that circulating T cells and monocytes contribute to cytokine production in sepsis caused by gram-positive bacteria.

GSK-3beta inhibitors attenuate the organ injury/dysfunction caused by endotoxemia in the rat

OBJECTIVE

Serine-threonine protein kinase glycogen synthase kinase (GSK)-3 is involved in regulation of many cell functions, but its role in regulation of inflammatory response is unknown. Here we investigate the effects of GSK-3beta inhibition on organ injury/dysfunction caused by lipopolysaccharide or coadministration of lipopolysaccharide and peptidoglycan in the rat.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Ninety-nine anesthetized male Wistar rats.

INTERVENTIONS

Study 1: Rats received either intravenous Escherichia coli lipopolysaccharide (6 mg/kg) or vehicle (1 mL/kg; saline). Study 2: Rats received either intravenous E. coli lipopolysaccharide (1 mg/kg) and Staphylococcus aureus peptidoglycan (0.3 mg/kg) or vehicle. The potent and selective GSK-3beta inhibitors TDZD-8 (1 mg/kg intravenously), SB216763 (0.6 mg/kg intravenously), and SB415286 (1 mg/kg intravenously) or vehicle (10% dimethyl sulfoxide) was administered 30 mins before lipopolysaccharide or lipopolysaccharide and peptidoglycan.

MEASUREMENTS AND MAIN RESULTS

Endotoxemia resulted in increases in the serum levels of creatinine (indicator of renal dysfunction), aspartate aminotransferase, alanine aminotransferase (markers for hepatocellular injury), lipase (indicator of pancreatic injury), and creatine kinase (indicator of neuromuscular injury). Coadministration of lipopolysaccharide and peptidoglycan resulted in hepatocellular injury and renal dysfunction. All GSK-3beta inhibitors attenuated the organ injury/dysfunction caused by lipopolysaccharide or lipopolysaccharide and peptidoglycan. GSK-3beta inhibition reduced the Ser536 phosphorylation of nuclear factor-kappaB subunit p65 and the messenger RNA expression of nuclear factor-kappaB-dependent proinflammatory mediators but had no effect on the nuclear factor-kappaB/DNA binding activity in the lung. GSK-3beta inhibition reduced the increase in nuclear factor-kappaB p65 activity caused by interleukin-1 in human embryonic kidney cells in vitro.

CONCLUSIONS

The potent and selective GSK-3beta inhibitors TDZD-8, SB216763, and SB415286 reduced the organ injury/dysfunction caused by lipopolysaccharide or lipopolysaccharide and peptidoglycan in the rat. We propose that GSK-3beta inhibition may be useful in the therapy of the organ injury/dysfunction associated with sepsis, shock, and other diseases associated with local or systemic inflammation.

The effect of innate immunity on autoimmune diabetes and the expression of Toll-like receptors on pancreatic islets

Viral infections have previously been implicated as a trigger of autoimmune diabetes. In this study, we compared a viral mimic with other microbial components derived from bacteria in triggering diabetes development in C57BL/6-rat insulin promoter-B7.1 mice that do not normally develop diabetes. It is striking that only the viral mimic induced the development of diabetes in our model system. Further mechanistic studies suggest that diabetes is induced, in part, by the combination of direct recognition of this virus-like stimulus by pancreatic islets through the expression of the innate immune receptor, Toll-like receptor 3. In addition, the functions of APCs are up-regulated, and this could stimulate islet Ag-reactive T cells that will attack beta cells leading to autoimmune diabetes.

Proinflammatory bacterial peptidoglycan as a cofactor for the development of central nervous system autoimmune disease

Upon stimulation by microbial products through TLR, dendritic cells (DC) acquire the capacity to prime naive T cells and to initiate a proinflammatory immune response. Recently, we have shown that APC within the CNS of multiple sclerosis (MS) patients contain peptidoglycan (PGN), a major cell wall component of Gram-positive bacteria, which signals through TLR and NOD. In this study, we report that Staphylococcus aureus PGN as a single component can support the induction of experimental autoimmune encephalomyelitis (EAE) in mice, an animal model for MS. Mice immunized with an encephalitogenic myelin oligodendrocyte glycoprotein peptide in IFA did not develop EAE. In contrast, addition of PGN to the emulsion was sufficient for priming of autoreactive Th1 cells and development of EAE. In vitro studies demonstrate that PGN stimulates DC-mediated processes, reflected by increased Ag uptake, DC maturation, Th1 cell expansion, activation, and proinflammatory cytokine production. These data indicate that PGN-mediated interactions result in proinflammatory stimulation of Ag-specific effector functions, which are important in the development of EAE. These PGN-mediated processes may occur both within the peripheral lymph nodes as well as in the CNS and likely involve recognition by TLR on DC. Thus, PGN may provide a physiological trigger of DC maturation, and in this way disrupt the normal tolerance to self Ag. As such, PGN signaling pathways may serve as novel targets for the treatment of MS.

Airway peptidoglycan and immunostimulatory DNA exposures have divergent effects on the development of airway allergen hypersensitivities

BACKGROUND

Environmental exposures to toll-like receptor (TLR) ligands have been suggested to provide immunologic protection against allergic diseases. However, some TLRs use unique intracellular signaling pathways, suggesting that ambient TLR ligand exposures might induce a range of host responses.

OBJECTIVE

These investigations compared peptidoglycan (PGN; TLR2)-induced and immunostimulatory sequence DNA oligodeoxynucleotide (ISS-ODN; TLR9)-induced innate responses and determined how airway exposures to these TLR ligands affect adaptive immunity and the asthmatic phenotype.

METHODS

In in vitro and in vivo studies innate responses to PGN and ISS-ODN were compared. Alternatively, mice were intranasally immunized with ovalbumin (OVA) alone or OVA plus PGN or ISS-ODN, and adaptive immune profiles and responses to airway OVA challenge were assessed.

RESULTS

PGN and ISS-ODN induced divergent innate responses predictive of their having TH2- and TH1-biasing adjuvant potential, respectively. Consistent with these findings, mice intranasally immunized with OVA alone had relatively weak adaptive responses, whereas intranasal OVA/PGN- and OVA/ISS-ODN-coimmunized mice had much stronger humoral and cellular responses that were TH2 and TH1 biased, respectively. Finally, on airway allergen challenge, mice intranasally immunized with OVA alone had modest TH2-biased airway hypersensitivity responses, whereas airway responses were greatly exaggerated for intranasal OVA/PGN-immunized mice. In contrast, intranasal OVA/ISS-ODN-immunized mice had little evidence of airway hypersensitivity after airway allergen challenge.

CONCLUSIONS

Considered in a larger context, these results suggest that inspired air is likely to contain TLR ligands capable of both preventing and precipitating the asthmatic phenotype.

Lipoteichoic acid downregulates FcepsilonRI expression on human mast cells through Toll-like receptor 2

BACKGROUND

FcepsilonRI on the surface of mast cells (MCs) plays a central role in allergic responses. Recent evidence shows that exposure to microbial components corresponds with a significant reduction in the risk for allergic diseases. Although many reports suggest that this is due to changes in T-cell functions, how MC functions are altered by bacterial infection remains unknown.

OBJECTIVE

We sought to elucidate the effect of bacterial infection on MC function and expression of Fc receptors, such as FcepsilonRI.

METHODS

Isolated human pulmonary MCs and a human MC line (LAD2) were stimulated with bacterial components, and the function and surface expression of Fc receptors were measured.

RESULTS

Lipoteichoic acid (LTA) and peptidoglycan, but not LPS, flagellin, or 3CpG-oligodeoxynucleotide, reduced the expression of FcepsilonRI on LAD2 cells. An antibody to Toll-like receptor (TLR) 2 partially blocked the effect of LTA but not peptidoglycan. Both LTA and peptidoglycan reduced MC degranulation caused by an antigen-specific IgE. Furthermore, exposure of pulmonary MCs to LTA reduced both FcepsilonRI expression and IgE-induced degranulation. None of the bacterial components affected the expression of other Fc receptors, such as Fcgamma receptors or Fcalpha receptor I.

CONCLUSIONS

Our results indicate that LTA reduces the surface expression of FcepsilonRI through TLR2 and suggests that TLR2 ligands could be used as a novel therapy for controlling allergic disorders.

CLINICAL IMPLICATIONS

By knowing how bacterial components modulate MC function, we can expand our possibilities for therapeutic interventions of allergic diseases.

Peptidoglycan of Staphylococcus aureus causes inflammation and organ injury in the rat*

OBJECTIVE

Previous studies have implicated a role of peptidoglycan in the pathophysiology of organ injury in sepsis. However, the systemic response to, and organ injury caused by, peptidoglycan have been scarcely studied in vivo.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Fifty-seven anesthetized, male Wistar rats.

INTERVENTIONS

After surgical preparation, anaesthetized rats were administered 3 mg/kg Staphylococcus aureus peptidoglycan (n = 9), 10 mg/kg S. aureus peptidoglycan (n = 14), or an equal volume of saline (sham, n = 12) in the jugular vein over a 10-min period.

MEASUREMENTS AND MAIN RESULTS

Injection of low-dose peptidoglycan (3 mg/kg) had no measurable effects on the rats. In contrast, high-dose peptidoglycan (10 mg/kg) caused increased serum values of aspartate aminotransferase (p < or =.005), alanine aminotransferase (p < or =.001), gamma-glutamyltransferase, and bilirubin (p < or =.05) (indicators of liver injury/dysfunction) as well as a moderate, but significant, increase in serum creatinine and urea (p < or =.05) (indicators of renal dysfunction). Plasma analyses showed a substantial increase in plasma values of tumor necrosis factor-alpha, interleukin-6, and interleukin-10 (p < or =.05 for all vs. sham) at 1 and 3 hrs (enzyme-linked immunosorbent assay). This was accompanied by accumulation of messenger RNAs for tumor necrosis factor-alpha, interleukin-6, and interleukin-10 in both the liver and the lung (p < or =.05 for all cytokines vs. sham) (real-time polymerase chain reaction). Peptidoglycan also caused increased DNA binding of nuclear factor-kappaB (band-shift assays) and phosphorylation of c-Jun and Jun N-terminal kinase (Western blots). In the kidney, interleukin-6 messenger RNA was increased, whereas Toll-like receptor 4 messenger RNA was significantly decreased.

CONCLUSIONS

These results demonstrate that injection of peptidoglycan alone causes organ injury/dysfunction, organ inflammation, and systemic inflammation in the rat, involving nuclear factor-kappaB and possibly activator protein 1. These data support the contention that peptidoglycan is a contributing factor in the pathophysiology of organ injury in sepsis.

Mast cells play a crucial role in Staphylococcus aureus peptidoglycan-induced diarrhea

Bacterium-induced diarrhea results in 2 to 2.5 million deaths in the world each year. The mechanism needs to be further understood. Staphylococcus aureus infection has a close relation with diarrhea; its cell wall component peptidoglycan (PGN) has strong biological activity on immune cells and possibly plays a role in S. aureus-induced diarrhea. The present study showed that oral PGN-induced diarrhea in mice in a dose-dependent manner. Intestinal epithelial cells absorbed PGN via the intracellular pathway. Intestinal mast cells were activated after PGN gavage. Toll-like receptor (TLR)2 expression was detected in mast cells in the intestine as well as in the murine mast cell line p815 cells. Blocking TLR2 or nucleotide-binding oligomerization domain (NOD)1 with related antibodies or RNA interference abolished PGN-induced p815 cell activation. The mast cell mediator histamine and serotonin had synergistic effects in PGN-induced diarrhea. In summary, oral PGN can induce diarrhea in mice, and TLR2 and NOD1 mediate the PGN-induced mast cell activation that plays a critical role in diarrhea induction. Blockade of TLR2 or NOD1 or treating mice with a mast cell stabilizer can efficiently inhibit PGN-induced-diarrhea, providing potential therapeutic significance.

Trunk kidney of grass carp (Ctenopharyngodon idella) mediates immune responses against GCRV and viral/bacterial PAMPs in vivo and in vitro

Trunk kidney is a vital organ for excretion in teleosts. There have been sporadic reports of processing pathogens for the immune function in trunk kidney. However, molecular processes of pathogen recognition receptors (PRRs) responding to virus and viral/bacterial pathogen-associated molecular patterns (PAMPs) are poorly elucidated in trunk kidney. In the present study, we investigated transcriptional profiles of twelve representative immune-related genes (TLRs (TLR3, TLR7 and TLR22); RLRs (RIG-I, MDA5 and LGP2); NLRs (NOD1 and NOD2); adapter molecules (MyD88 and IPS-1); effector molecule type I interferon (IFN-I) and immunoglobulin M (IgM)) in trunk kidney tissue of grass carp (Ctenopharyngodon idella) (designated as Ci) injection of grass carp reovirus (GCRV) utilizing quantitative real-time RT-PCR (qRT-PCR). Furthermore, mRNA expression patterns of these genes (IgM excepted) were examined post GCRV infection and polyinosine-polycytidylic acid (poly(I:C)), lipopolysaccharide (LPS) or peptidoglycan (PGN) stimulation in primary trunk kidney cells of grass carp. The relative values of CiTLR3, CiTLR22 and CiMyD88 were increased post GCRV challenge and viral/bacterial PAMPs stimulation. The mRNA transcriptions of CiTLR7 were obviously activated with GCRV challenge. Remarkably, the mRNA expressions of CiRIG-I, CiMDA5, CiLGP2 and CiIPS-1 were largely up-regulated with GCRV challenge and viral/bacterial PAMPs stimulation. Interestingly, the expression tendencies of CiNOD1 and CiNOD2 were differential not only in GCRV challenge and poly(I:C) stimulation, but also in LPS and PGN stimulation. It was demonstrated that CiIFN-I induced powerful anti-viral and anti-bacterial effects in trunk kidney. In addition, the expression of CiIgM was induced at 72 h post GCRV injection in vivo. Collectively, these results suggest that trunk kidney of grass carp serves as an important immune organ, and plays crucial roles in triggering anti-viral and anti-bacterial immune responses both in vivo and in vitro.

Ephedrine hydrochloride inhibits PGN-induced inflammatory responses by promoting IL-10 production and decreasing proinflammatory cytokine secretion via the PI3K/Akt/GSK3β pathway

Approaches for controlling inflammatory responses and reducing the mortality rate of septic patients remain clinically ineffective; new drugs need to be identified that can induce anti-inflammatory responses. Ephedrine hydrochloride (EH) is a compound that is widely used in cardiovascular diseases, especially to treat hypotension caused by either anesthesia or overdose of antihypertensive drugs. In this study, we reported that EH also plays an important role in the control of the inflammatory response. EH increased IL-10 and decreased proinflammatory cytokine (IL-6, tumor-necrosis factor (TNF)-α, IL-12 and IL-1β) expression in primary peritoneal macrophages and Raw264.7 cells treated with peptidoglycan (PGN), a Gram-positive cell wall component. The anti-inflammatory role of EH was also demonstrated in an experimental mouse model of peritonitis induced by intraperitoneal PGN injection. The phosphatidylinositol 3-kinase (PI3K)/Akt pathway was found to be responsible for the EH-mediated increase in IL-10 production and decrease in IL-6 expression. Therefore, our results illustrated that EH can help maintain immune equilibrium and diminish host damage by balancing the production of pro- and anti-inflammatory cytokines after PGN challenge. EH may be a new potential anti-inflammatory drug that can be useful for treating severe invasive Gram-positive bacterial infection.

Leptospira interrogans and Leptospira peptidoglycans induce the release of tumor necrosis factor alpha from human monocytes

Elevated plasma concentrations of the cytokine tumor necrosis factor alpha (TNF alpha) have been observed in patients affected by leptospirosis. In this study we found that a preparation of peptidoglycan of Leptospira interrogans, serovar copenhageni, was able to induce the release of TNF alpha from peripheral blood mononuclear cells. TNF alpha induction occurred in a dose dependent manner and was not affected by the endotoxin inhibitor polymixin B. This is the first report on induction of TNF alpha release by a peptidoglycan of spirochetes. Our findings are consistent with existing clinical data and provide a potential mechanism for TNF alpha production.

Lipoteichoic acid and lipopolysaccharide can activate antimicrobial peptide expression in the tobacco hornworm Manduca sexta

Activation of prophenoloxidase and synthesis of antimicrobial peptides (AMPs) are two important innate immune mechanisms in insects. In the current study, we investigated immune responses activated by three major bacterial components, lipopolysaccharide (LPS) (including rough mutants of LPS), lipoteichoic acid (LTA), and peptidoglycan (PG), in the larvae of a lepidopteran insect, Manduca sexta. We found that two DAP (diaminopimelic acid)-type PGs from Escherichia coli and Bacillus subtilis were much more potent than LPS and LTA from the respective bacteria as well as a Lysine-type PG in activation of prophenoloxidase in M. sexta larval plasma in vitro. Transcription levels of AMP genes, such as Attacin, Lebocin and Moricin genes, in the hemocytes and fat body of larvae were significantly induced by smooth LPS (TLR4grade) and rough mutants of LPS (TLRgrade), synthetic lipid A, LTA, and PG. LPS from E. coli and LTA from B. subtilis activated AMP expression to significantly higher levels than PGs from the respective bacterial strains, and smooth LPS were more potent than lipid A and rough mutants of LPS in activation of AMP expression. Our results demonstrated for the first time that LTA can activate AMP expression, and different moieties of LPS may synergistically activate AMP expression in M. sexta.

Peptidoglycan primes for LPS-induced release of proinflammatory cytokines in whole human blood

The pathophysiological mechanisms involved in mixed bacterial infections caused by gram-positive and gram-negative bacteria are largely unknown. The present study examines the potential interaction between lipopolysaccharide (LPS) and peptidoglycan (PepG) in the induction of the sepsis-associated cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and IL-10 in whole human blood. Plasma values of these cytokines were measured by enzyme immunoassays and a TNF bioassay. Co-administration of PepG (10 microg/mL) or muramyl dipeptide (MDP, 1 microg/mL) with LPS (10 ng/mL) caused significantly elevated values of TNF-alpha and IL-6 in the blood that could not be obtained by the sum of the values obtained by each stimulant alone, or by 3-fold higher doses of either bacterial component alone. This phenomenon was observed 1 h after stimulation, throughout the experimental period (24 h), and with different doses of LPS and PepG. In contrast, the release of IL-10 was not influenced by the co-administration of PepG or MDP with LPS. The TNF-alpha release induced by co-administration of LPS and PepG was abrogated after pretreatment with a monoclonal antibody against CD14 (18D11). Addition of PepG or MDP to whole blood caused a 2-fold increase in the surface expression of CD14 on monocytes, as measured by flow cytometry. In contrast, LPS caused decreased expression of this receptor. Our data suggest that PepG and MDP primes human whole blood leukocytes for LPS-induced release of proinflammatory cytokines. We speculate that synergy between PepG and LPS may contribute to the pathogenesis in sepsis caused by mixed bacterial infections.

Experimental uveitis. Elicited by peptidoglycan-polysaccharide complexes, lipopolysaccharide, and muramyl dipeptide

Uveitis could be a reaction to bacterial debris disseminated to the eye from extraocular sites of infection. In this study, we relate the composition of several bacterial components to their inflammatory properties in the eye. Groups of rabbits were injected intravitreously with peptidoglycan-polysaccharide (PG-PS) complexes isolated from group A streptococci, Escherichia coli lipopolysaccharide (LPS), or synthetic muramyl dipeptide (MDP). The lipid A region of LPS and the glycan backbone of PG are chemical analogues; MDP is the minimal biologically active subunit of PG. All of these molecules elicited uveitis as observed both clinically and histologically. The MDP elicited an acute inflammation characterized by a heterophil and monocyte infiltrate that subsided within 16 days. The PG-PS and LPS elicited chronic inflammation characterized by mononuclear and lymphocyte infiltration and severe necrosis of the retina.

The sulfated polysaccharide-peptidoglycan complex potently inhibits embryonic angiogenesis and tumor growth in the presence of cortisone acetate

In combination with cortisone acteate, the sulfated polysaccharide (SP)-peptidoglycan (PG) complex produced by an Arthrobacter species was found to inhibit both embryonic angiogenesis of chick chorioallantoic membrane (CAM) and growth of solid Sarcoma 180 tumor in mice. Three fractions obtained from the SP-PG complex by gel filtration showed a great difference in the inhibitory effect on angiogenesis of the CAM, whereas in ex vivo study such a difference was reduced. Of the three fractions, SP-PG-L having the lowest molecular weight and peptidoglycan content exhibited the highest antiangiogenic and antitumor activities, even higher than those of heparin. Neither desulfation nor sulfation of the SP-PG complex greatly affected the antiangiogenic activity, and dextran sulfates and mannoglucan sulfates were lacking the activity. This suggested that glycosyl sequences of sulfated polysaccharides are more important for the activity, rather than content or intramolecular distribution of sulfate groups.

The metabolic fate of 14C-labeled peptidoglycan monomer in mice. I. Identification of the monomer and the corresponding pentapeptide in urine

The distribution of radioactive products in mouse urine following intravenous administration of the 14C-labeled peptidoglycan monomer, GlcNAc-MurNaC-L-Ala-D-isoglutamine-meso-diaminopimelic acid-D-Ala-D-Ala, has been studied. 60--80% of radioactivity was recovered within first 3 h, 4--8% in the next 3 h and 2--7% in the following 18 h. The majority of the label was associated with the unchanged peptidoglycan monomer (42--56% of the dose). 14--21% of the label was incorporated into a compound which was isolated and tentatively identified as L-Ala-D-isoglutamine-meso-diaminopimelic acid-D-Ala-D-Ala. The kinetics of excretion and the distribution of radioactivity did not differ in immunized, when compared to non-immunized, mice.

15d-prostaglandin J2 reduces multiple organ failure caused by wall-fragment of Gram-positive and Gram-negative bacteria

Septic shock is still the major cause of death in surgical intensive care units. Both gram-positive (G+) and gram-negative (G-) bacteria have been isolated in the blood of a large portion of septic patients, and these polymicrobial infections often have a higher mortality than infections due to a single organism. Cell wall fragments from G+ and G- bacteria synergise to cause shock and multiple organ dysfunction in vivo (G+/G- shock). Male Wistar rats were anaesthetised and received a coadministration of wall fragments from G+ and G- bacteria, Staphilococcus aureus (S. aureus) peptidoglycan [0.3 mg/kg, intravenously (i.v.)] and Escherichia coli (E. coli) lipopolysaccharide (1 mg/kg, i.v.) or vehicle (saline, 1 ml/kg, i.v.). G+/G- shock for 6 h resulted in an increase in serum levels of creatinine (indicator of renal dysfunction), alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (gamma-GT), bilirubin (markers for hepatic injury and dysfunction) and creatine kinase (CK, an indicator of neuromuscular, skeletal muscle or cardiac injury). Pretreatment of rats with the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist 15d-prostaglandin J2 (0.3 mg/kg, i.v., 30 min prior to G+/G-) reduced the multiple organ injury/dysfunction caused by coadministration of peptidoglycan+lipopolysaccharide. The selective PPAR-gamma antagonist GW9662 (2-Chloro-5-nitrobenzanilide) (1 mg/kg, i.v., given 45 min prior to G+/G-) abolished the protective effects of 15d-prostaglandin J2. 15d- prostaglandin J2 did not affect the biphasic fall in blood pressure or the increase in heart rate caused by administration of peptidoglycan+lipopolysaccharide. The mechanism(s) of the protective effect of this cyclopentenone prostaglandin are-at least in part-PPAR-gamma dependent, as the protection afforded by 15d-prostaglandin J2 was reduced by the PPAR-gamma antagonist GW9662. We propose that 15d-prostaglandin J2 or other ligands for PPAR-gamma may be useful in the therapy of the organ injury associated with septic shock.

Gene expression profiles in the rat streptococcal cell wall-induced arthritis model identified using microarray analysis

Experimental arthritis models are considered valuable tools for delineating mechanisms of inflammation and autoimmune phenomena. Use of microarray-based methods represents a new and challenging approach that allows molecular dissection of complex autoimmune diseases such as arthritis. In order to characterize the temporal gene expression profile in joints from the reactivation model of streptococcal cell wall (SCW)-induced arthritis in Lewis (LEW/N) rats, total RNA was extracted from ankle joints from naïve, SCW injected, or phosphate buffered saline injected animals (time course study) and gene expression was analyzed using Affymetrix oligonucleotide microarray technology (RAE230A). After normalization and statistical analysis of data, 631 differentially expressed genes were sorted into clusters based on their levels and kinetics of expression using Spotfire^® profile search and K-mean cluster analysis. Microarray-based data for a subset of genes were validated using real-time PCR TaqMan^® analysis. Analysis of the microarray data identified 631 genes (441 upregulated and 190 downregulated) that were differentially expressed (Delta > 1.8, P < 0.01), showing specific levels and patterns of gene expression. The genes exhibiting the highest fold increase in expression on days -13.8, -13, or 3 were involved in chemotaxis, inflammatory response, cell adhesion and extracellular matrix remodelling. Transcriptome analysis identified 10 upregulated genes (Delta > 5), which have not previously been associated with arthritis pathology and are located in genomic regions associated with autoimmune disease. The majority of the downregulated genes were associated with metabolism, transport and regulation of muscle development. In conclusion, the present study describes the temporal expression of multiple disease-associated genes with potential pathophysiological roles in the reactivation model of SCW-induced arthritis in Lewis (LEW/N) rat. These findings improve our understanding of the molecular events that underlie the pathology in this animal model, which is potentially a valuable comparator to human rheumatoid arthritis (RA).

Sympathetic nervous modulation of the skin innate and adaptive immune response to peptidoglycan but not lipopolysaccharide: involvement of beta-adrenoceptors and relevance in inflammatory diseases

Disorders of the skin immune activity are implicated in the pathogenesis of acquired inflammatory skin disorders. Inflammatory diseases including psoriasis, atopic dermatitis, lichen planus and vitiligo have also been associated with local alterations of adrenergic mechanisms and emotional stress. Here we show that the beta-adrenergic receptors antagonist propranolol along with peptidoglycan, but not LPS, combined with intradermal injection of a soluble protein, shifted the recall memory response to the Th1 type. The specific beta2-AR antagonist ICI 118,551 did not reproduce this effect suggesting that inhibition of both beta1- and beta2-AR caused the Th1 polarization. The underlying mechanism included enhanced local expression of IFN-gamma, IL-12 and IL-23 as well as of IFN-beta and CXCR3 ligands during the innate phase of the response which resulted in an increase of antigen-positive plasmacytoid dendritic cells (pDCs) in the draining lymph node. In particular, modulation of inflammatory cytokines, and IFN-beta inducible genes expression appeared to involve also the beta1-AR. Plasmacytoid dendritic cells and IL-23 were recently reported to play a central role in the pathogenesis of Th1-sustained inflammatory skin diseases such as psoriasis. Thus, primary beta-adrenoceptors signaling defects or altered sympathetic nervous activity together with selected pattern recognition receptors activation might serve as initiation and/or persistence factors for numerous Th1-sustained inflammatory skin diseases.

The synergistic effect of peptidoglycan and lipopolysaccaride on osteoclast formation

PURPOSE

The purpose of this study was to investigate the mechanisms leading to periapical tissue destruction by the Gram-positive bacterial cell component, peptidoglycan (PGN) and Gram-negative bacterial cell component lipopolysaccaride (LPS).

STUDY DESIGN

Osteoclast precursor RAW 264.7 cells were cultured with 50 ng/ml receptor activator of NF-kappaB ligand (RANKL) for 72 hours. RANKL was then removed and the cells were treated with various concentrations of PGN in the presence or absence of various concentration of LPS for an additional 48 hours. RT-PCR analysis was performed to examine the presence of receptors on osteoclasts known to be involved in mediating cellular activation in response to PGN (TLR2) and LPS (TLR 4).

RESULTS

PGN dose dependently and reproducibly stimulated TRAP-positive multinucleated osteoclast-like (OCL) cell formation. PGN and LPS had synergistic effects on the induction of OCL cell formation. Both unstimulated and RANKL-stimulated RAW 264.7 cells expressed TLR2 and TLR4 mRNA.

CONCLUSION

The results underscore the importance of considering both Gram-positive and Gram-negative bacteria when interpreting findings associated with primary and secondary periapical lesions.

Cytokine and nitric oxide production in the acute phase of bacterial cell wall-induced arthritis

We have investigated the temporal relationship among proinflammatory cytokine expression, nitric oxide (NO) production and joint inflammation in the acute phase of bacterial cell wall-derived peptidoglycan polysaccharide (PG/PS)-induced arthritis. Acute joint inflammation was induced in female LEW/N rats by a single intraperitoneal injection of PG/PS. Arthritis index and paw volume were quantified and joint histopathology was evaluated during acute joint inflammation (0-10 days). Tumor necrosis factor (TNF), interleukin-1 (IL-1) and interleukin-6 (IL-6) were determined by bioassay whereas nitric oxide (NO) was quantified by measuring serum nitrate/nitrite levels via the Griess procedure. We found that serum levels of TNF and serum IL-1 preceded the increase in IL-6 and NO production. Furthermore, the production of these proinflammatory cytokines and NO preceded bone erosion and osteoclast activity. Erosion of subchondral bone preceded pannus formation and cellular synovitis in the acute phase of PG/PS-induced arthritis. The temporal expression of TNF, IL-1, IL-6 and NO suggest a cascade of inflammatory mediators in which monocytes and macrophages respond to PG/PS with enhanced synthesis of TNF and IL-1, which may in turn promote the synthesis of IL-6 and NO. We postulate that one or more of these inflammatory events are responsible for initiating the subchondral bone erosion observed in acute joint inflammation.

Comparative immune responses to native cell envelope antigens and the hot sodium dodecyl sulfate insoluble fraction (PG) of Brucella abortus in cattle and mice

Brucella abortus vaccines composed of native cell envelopes or outer membrane proteins of smooth strain 2308 were compared with a vaccine (PG) composed of the insoluble residue of strain 2308 cell envelopes which had been extracted with hot sodium dodecyl sulfate. Vaccines were given by injection in an oil base adjuvant containing trehalose dimycolate and muramyl dipeptide or without adjuvant. Mice vaccinated with 30 micrograms native cell envelopes or PG and challenged 4 weeks later with virulent B. abortus strain 2308 displayed equivalent levels of protective immunity at 1 and 4 weeks post-infection. Heifers were vaccinated with 5 mg of antigens in adjuvant; PG was also administered without adjuvant. Humoral and cell mediated immune (CMI) responses were tested at monthly intervals. PG without adjuvant induced negligible immune responses. Native cell envelope antigens induced significantly higher titers of whole cell agglutinins over a 3-month period than did PG, although revaccination with PG in adjuvant enhanced the production of agglutinins and both vaccines induced antibodies to the O polysaccharide. Lymphocyte blastogenesis responses and delayed hypersensitivity reactions to porin and group 3 proteins were stimulated by both native and PG vaccines, and the magnitude of the responses did not differ significantly between the treatment groups. These vaccines were therefore comparable in their capacity to induce protective immunity in mice and CMI responses in cattle, whereas antibody responses induced by PG in cattle were generally lower. These findings provide a basis for evaluation of nonliving B. abortus vaccines in cattle.

Effect of Liposomal Formulations and Immunostimulating Peptidoglycan Monomer (PGM) on the Immune Reaction to Ovalbumin in Mice

The adjuvant activity of liposomes and immunostimulating peptidoglycan monomer (PGM) in different formulations has been studied in mice model using ovalbumin (OVA) as an antigen. PGM is a natural compound of bacterial origin with well-defined chemical structure: GlcNAc-MurNAc-L-Ala-D-isoGln-mesoDpm(epsilonNH2)-D-Ala-D-Ala. It is a non-toxic, non-pyrogenic, and water-soluble immunostimulator. The aim of this study was to investigate the influence of different liposomal formulations of OVA, with or without PGM, on the production of total IgG, as well as of IgG1 and IgG2a subclasses of OVA-specific antibodies (as indicators of Th2 and Th1 type of immune response, respectively). CBA mice were immunized s.c. with OVA mixed with liposomes, OVA with PGM mixed with liposomes, OVA encapsulated into liposomes and OVA with PGM encapsulated into liposomes. Control groups were OVA in saline, OVA with PGM in saline, and OVA in CFA/IFA adjuvant formulation. The entrapment efficacy of OVA was monitored by HPLC method. The adjuvant activity of the mixture of OVA and empty liposomes, the mixture of OVA, PGM, and liposomes and PGM encapsulated with OVA into liposomes on production of total anti-OVA IgG was demonstrated. The mixture of PGM and liposomes exhibited additive immunostimulating effect on the production of antigen-specific IgGs. The analysis of IgG subclasses revealed that encapsulation of OVA into liposomes favors the stimulation of IgG2a antibodies, indicating the switch toward the Th1 type of immune response. When encapsulated into liposomes or mixed with liposomes, PGM induced a switch from Th1 to Th2 type of immune response. It could be concluded that appropriate formulations of antigen, PGM, and liposomes differently affect the humoral immune response and direct the switch in the type of immune response (Th1/Th2).

Pretreatment with the Gram-positive bacterial cell wall molecule peptidoglycan improves bacterial clearance and decreases inflammation and mortality in mice challenged with Pseudomonas aeruginosa

The objective of this study was to determine if inflammatory tolerance and enhancement of innate immune function could be induced by the Gram-positive cell wall component peptidoglycan (PGN). Male mice (C57BL6/J or C3H/HeJ, 8-12 weeks of age) were given intraperitoneal injections of 1mg PGN on 2 consecutive days. The mice were then challenged with lipopolysaccharide (LPS) or live Pseudomonas aeruginosa (1 x 10(8) colony-forming units) 2 days after the second pretreatment. Mice pretreated with PGN had diminished plasma concentrations of TNFalpha and IFNgamma and elevated concentrations of IL-10 in response to a subsequent LPS or Pseudomonas challenge when compared to untreated controls. Bacterial clearance was improved in mice pretreated with PGN, and mortality in response to a subsequent Pseudomonas challenge was significantly attenuated. PGN pretreatment of LPS-unresponsive mice (C3H/HeJ) verified that the effect of PGN pretreatment was not due to any LPS contamination. We have previously demonstrated that PGN pretreatment induced resistance to a Gram-positive bacterial challenge. The present study extends those results by showing that exposure to the Gram-positive bacterial cell wall component peptidoglycan also induces cross-tolerance to LPS and non-specifically enhances innate immune function in that PGN-pretreated mice had increased resistance to Gram-negative bacterial challenge.