Lipopolysaccharide dependent cellular activation

Purification and Biological Function of Caldecrin

Blood calcium homeostasis is critical for biological function. Caldecrin, or chymotrypsin-like elastase, was originally identified in the pancreas as a serum calcium-decreasing factor. The serum calcium-decreasing activity of caldecrin requires the trypsin-mediated activation of the protein. Protease activity-deficient mature caldecrin can also reduce serum calcium concentration, indicating that structural processing is necessary for serum calcium-decreasing activity. Caldecrin suppresses the differentiation of bone-resorbing osteoclasts from bone marrow macrophages (BMMs) by inhibiting receptor activator of NF-κB ligand (RANKL)-induced nuclear factor of activated T-cell cytoplasmic 1 expression via the Syk-PLCγ-Ca2+ oscillation-calcineurin signaling pathway. It also suppresses mature osteoclastic bone resorption by RANKL-stimulated TRAF6-c-Src-Syk-calcium entry and actin ring formation. Caldecrin inhibits lipopolysaccharide (LPS)-induced osteoclast formation in RANKL-primed BMMs by inducing the NF-κB negative regulator A20. In addition, caldecrin suppresses LPS-mediated M1 macrophage polarization through the immunoreceptor triggering receptor expressed on myeloid cells (TREM) 2, suggesting that caldecrin may function as an anti-osteoclastogenic and anti-inflammatory factor via TREM2. The ectopic intramuscular expression of caldecrin cDNA prevents bone resorption in ovariectomized mice, and the administration of caldecrin protein also prevents skeletal muscle destruction in dystrophic mice. In vivo and in vitro studies have indicated that caldecrin is a unique multifunctional protease and a possible therapeutic target for skeletal and inflammatory diseases.

Role of p38 Mitogen-Activated Protein Kinase (MAPK) for Vacuole Formation in Lipopolysaccharide (LPS)-Stimulated Macrophages

The role of p38 mitogen-activated protein kinase (MAPK) on vacuole formation in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells was examined. LPS definitely induced the formation of vacuoles in RAW 264.7 cells and SB202190 as a p38 specific inhibitor also induced slight vacuole formation. The simultaneous treatment with LPS and SB202190 induced many more vacuoles in RAW 264.7 cells than the treatment with LPS or SB202190 alone, and the vacuoles were extraordinarily large in size. On the other hand, an inactive inhibitor of p38 MAPK did not augment LPS-induced vacuole formation. Further, the inhibitors of other MAPKs and nuclear factor (NF)-kappaB pathways did not affect it. The extraordinarily large vacuoles in RAW 264.7 cells treated with LPS and SB202190 were possibly formed via fusion of small vacuoles. However, SB202190 did not augment vacuole formation in CpG DNA or interferon (IFN)-gamma-stimulated RAW 264.7 cells. The role of p38 MAPK in the vacuole formation in LPS-stimulated macrophages is discussed.

Porphyromonas gingivalis LPS stimulates the expression of LPS-binding protein in human oral keratinocytes in vitro

LPS-binding protein (LBP) functions as a crucial molecule in innate immune responses to bacterial challenge. Our study has shown the expression of LBP in human gingiva and its significant association with periodontal health and disease. Porphyromonas gingivalis is a key pathogen of periodontal disease. P. gingivalis LPS as a main virulence factor is strongly involved in periodontal pathogenesis and it displays a significant lipid A structural heterogeneity. Currently, it remains unknown whether, and to what extent, the lipid A structural heterogeneity of P. gingivalis LPS affects LBP expression. The present study investigated the expression profile of LBP in human oral keratinocytes (HOKs) stimulated by two isoforms of P. gingivalis LPS [tetra- (LPS(1435/1449)) and penta-acylated (LPS(1690))] and Escherichia coli LPS, and the involvement of TLRs in LBP expression. The results showed that the expression of LBP mRNA and peptide was significantly up-regulated by P. gingivalis LPS(1690) and E. coli LPS, while P. gingivalis LPS(1435/1449) did not affect LBP expression. Blocking assay and siRNA gene silencing revealed that P. gingivalis LPS(1690)-induced LBP expression was through both TLR2 and TLR4. This in vitro study demonstrates that P. gingivalis LPS with a lipid A structural heterogeneity differentially modulates LBP expression in HOKs.

Specificity of antimicrobial peptide LL-37 to neutralize periodontopathogenic lipopolysaccharide activity in human oral fibroblasts

BACKGROUND

The antimicrobial peptide LL-37 is known to have a potent lipopolysaccharide (LPS)-neutralizing activity in various cell types. Because of observed heterogeneity within periodontopathogenic LPS, the authors hypothesized that LL-37 had specificity to neutralize such LPS activity. The present study, therefore, aims to investigate the LPS-neutralizing activity of LL-37 to various periodontopathogenic LPS in interleukin-8 (IL-8) production after challenging them in human oral fibroblasts.

METHODS

Human periodontal ligament fibroblasts (PDLF) and gingival fibroblasts (GF) were cultured from biopsies of periodontal ligament and gingival tissues. After cell confluence in 24-well plates, LPS (10 μg/mL) from Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans were added with or without LL-37 (10 μg/mL). After 18 hours, the supernatant was collected and analyzed in IL-8 production by enzyme-linked immunosorbent assay.

RESULTS

All periodontopathogenic LPS statistically significantly induced IL-8 production in both PDLF and GF (P <0.01). After neutralization with LL-37, both PDLF and GF showed a statistically significant reduction in IL-8 production compared with LPS-treated groups without LL-37 (P <0.01), and the percentage of reduction in IL-8 production in PDLF appeared to be higher than in GF. In addition, the percentage of reduction in IL-8 production varied considerably according to each periodontopathogenic LPS.

CONCLUSIONS

The antimicrobial peptide LL-37 had an ability to suppress periodontopathogenic LPS-induced IL-8 production in both PDLF and GF. Its LPS-neutralizing activity revealed specificity to periodontopathogenic LPS and seemed to be dependent on the heterogeneity within LPS between different genera.

Differential modulation of human {beta}-defensins expression in human gingival epithelia by Porphyromonas gingivalis lipopolysaccharide with tetra- and penta-acylated lipid A structures

Porphyromonas gingivalis lipopolysaccharide (LPS) is a crucial virulence factor strongly involved in the development of chronic periodontitis. It displays a significant amount of lipid A structural heterogeneity, containing both tetra- (LPS(1435/1449) ) and penta-acylated (LPS( 1690)) lipid A structures with opposing effects on E-selectin expression in human endothelial cells. Little is known about how these two isoforms of P. gingivalis LPS could differentially affect host innate immune responses in human gingival epithelia. The present study compares the modulatory effects of P. gingivalis LPS(1435/1449) and LPS(1690) on the expression of human beta-defensins (hBDs) in the reconstituted human gingival epithelium, and examines the involvements of a panel of pattern recognition receptors in the modulatory effects concerned. It is shown that hBD-1, hBD-2 and hBD-3 mRNAs are significantly up-regulated by P. gingivalis LPS(1690), but down-regulated by P. gingivalis LPS( 1435/1449). Toll-like receptor (TLR) 2 and CD14 mRNAs are also differentially regulated, and the modulation of hBD-2 expression may be through the co-operation of both TLR2 and TLR4. This study suggests that P. gingivalis LPS with different lipid A structures could differentially modulate host innate immune responses in human gingival epithelia, which may be a hitherto undescribed novel pathogenic mechanism of P. gingivalis in periodontal pathogenesis.

In vivo response to cross-linked polyethylene and polycarbonate-urethane particles

This study was undertaken to examine macrophage response to polycarbonate-urethane, a proposed alternative material to polyethylene in acetabular components of total hip arthroplasty. Polyethylene wear debris from total joint replacements has been linked to osteolysis and implant lifespan. It has been shown in vitro, that polyethylene particles cleaned of endotoxin generate less of an inflammatory cytokine response than endotoxin bound particles. Comparative particle induced effects on implant fixation were tested using endotoxin free cross-linked ultra-high molecular weight polyethylene (x-UHMWPE) and polycarbonate-urethane (PCU) particles with and without intraperitoneal injection (IP) of lipopolysaccharide (LPS) using a Ti-alloy femoral intramedullary nail rat model. MicroCT and mechanical testing assessment of peri-implant bone indicated significantly less bone and lower fixation strength, respectively, when the implant was surrounded by xUHMWPE particles compared to PCU particles (with and without LPS IP). This indicates particles of PCU may be less disruptive to bone-implant fixation than x-UHMWPE in vivo, under both LPS free and challenged conditions.

Interactions among genes influencing bacterial recognition increase IBD risk in a population-based New Zealand cohort

Bacterial sensing is crucial for appropriate response by the innate and adaptive immune system against invading microorganisms. Single nucleotide polymorphisms (SNPs) in genes involved in bacterial recognition, CARD15 and TLR4, increased the risk of inflammatory bowel disease (IBD) in a New Zealand Caucasian case-control cohort. We now consider the effects of SNPs in CD14, TLR9, and BPI, analyzed individually, in association with one another, and with SNPs in CARD15 or TLR4 in this same population group. SNPs in CD14 (c.-159 C>T), TLR9 (c.-1237T>C) and BPI (c.645A>G) showed no significant allele or genotype frequency differences between IBD cases and controls. Genotype-phenotype mapping reveals an association with BPI and ileocolonic Crohn's disease (CD) as well as an association with CD14 and early-onset ulcerative colitis (UC). Genotype interaction analyses using three different statistical approaches provided significant evidence of interaction for the following combinations: CARD15/TLR4 (CD and UC), CARD15/CD14 (CD and UC), CD14/TLR4 (UC only), and CD14/BPI (UC only). A trend for an association between BPI and TLR4 was observed in UC patients, but failed to reach statistical significance. Our findings support the idea of gene-gene interactions for genes involved in closely related pathways (i.e. bacterial detection). There is evidence that carrying two SNPs in genes may lead to statistical significance for genes and SNPs that do not otherwise confirm as risk alleles for disease aetiology when analysed alone.

Chemokines gene expression of RAW 264.7 cells by Actinobacillus actinomycetemcomitans lipopolysaccharide using microarray and RT-PCR analysis

Actinobacillus actinoinycetemcomitans (A. actinomycetem-comitans) is an important pathogen casuing aggressive periodontitis. The present study was designed to investigate the chemokines expression regulated by A. actinomycetemcomitans lipopolysaccharide (LPS). Chemokines genes expression profiling was performed in Raw 264.7 cells by analyses of microarray and reverse transcription-polymerase chain reaction (RT-PCR). Microarray results showed that the induction of monocyte chemoattractant protein-1alpha (MCP-1alpha) and macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, MIP-1gamma, regulated upon activation, normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein-2 (MIP-2), and interferon-gamma inducible protein 10 (IP 10) by A. actinomycetemcomitans LPS was increased to 12.5, 1.53, 9.09, 17.3, 2.82, 16.1, and 18.1 folds at 18 h, respectively. To check these chemokines expression by A. actinomycetemcomitans LPS, we examined gene expressions by RT-PCR, and found that the expression of MIP-1beta, MIP-1gamma, RANTES, MIP-2, and IP 10 was increased 107.1, 93.6, 106.8, 86.5, and 162.0 folds at 18 h, respectively. These results indicate that A. actinomycetemcomitans LPS stimulates the several chemokines expressions (MIP-1alpha, MIP-1beta, MIP-1gamma, RANTES, MIP-2, and IP 10) in Raw 264.7 cells.

Porphyromonas gingivalis, periodontal pathogen, lipopolysaccharide induces angiogenesis via extracellular signal-regulated kinase 1/2 activation in human vascular endothelial cells

Porphyromonas gingivalis is a major periodontal pathogen. The lipopolysaccharide (LPS) secreted from P. gingivalis is implicated in the initiation and progression of periodontitis. Aberrant angiogenesis is often associated with lesion formation in chronic periodontitis. In this study, we report that P. gingivalis LPS activates angiogenic cascade, migration, invasion and tube formation in human umbilical vein endothelial cells (HUVECs). Furthermore, P. gingivalis LPS potently stimulated in vivo neovascularization in chick chorioallantoic membrane (CAM) and the mouse Matrigel plug assay. P. gingivalis LPS had no effect on the expression of vascular endothelial growth factor (VEGF) or its receptor, Flk-1, implying that P. gingivalis LPS-induced angiogenesis may result from its direct action on endothelial cells. P. gingivalis LPS evoked activation of the mitogen-activated protein kinase ERK1/2 in HUVECs, which is closely linked to angiogenesis. Taken together, these results strongly suggest P. gingivalis LPS plays an important role in the pathological angiogenesis for periodontal diseases, such as periodontitis.

Toll-like receptors and chondrocytes: The lipopolysaccharide-induced decrease in cartilage matrix synthesis is dependent on the presence of toll-like receptor 4 and antagonized by bone morphogenetic protein 7

OBJECTIVE

To assess the presence of Toll-like receptors (TLRs) 1-9 in human articular cartilage, and to investigate the effects of lipopolysaccharide (LPS)-induced activation of TLR-4 on biosynthetic activity and matrix production by human articular chondrocytes.

METHODS

TLRs 1-9 were assessed in human articular cartilage by reverse transcription-polymerase chain reaction (RT-PCR); TLR-4 was also analyzed by Western blotting and immunohistochemistry. Articular chondrocytes were isolated from human donors and from wild-type or TLR-4(-/-) mice. Chondrocyte monolayer cultures were incubated with interleukin-1beta (IL-1beta) and LPS in the absence or presence of bone morphogenetic protein 7 (BMP-7) and IL-1 receptor antagonist (IL-1Ra). Neosynthesis of sulfated glycosaminoglycans (sGAG) was measured by (35)S-sulfate incorporation. Endogenous gene expression of cartilage markers as well as IL-1beta was examined using RT-PCR. The involvement of p38 kinase or p44/42 kinase (ERK-1/2) in LPS-mediated TLR-4 signaling was investigated by immunoblotting, RT-PCR, and sGAG synthesis.

RESULTS

TLRs 1-9 were found on the messenger RNA (mRNA) level in human articular chondrocytes. The presence of TLR-4 was also observed on the protein level. In murine and human articular chondrocytes, but not in chondrocytes derived from TLR-4(-/-) mice, stimulation with LPS resulted in a decrease in total proteoglycan synthesis. IL-1beta mRNA expression was increased by TLR-4 activation, whereas expression of aggrecan and type II collagen was significantly decreased. The presence of BMP-7 and IL-1Ra antagonized the anti-anabolic effects of LPS. Blocking of p38, but not ERK-1/2, resulted in inhibition of both LPS-mediated IL-1beta gene expression and the negative effects of LPS on matrix biosynthesis.

CONCLUSION

These data demonstrate the presence of TLRs in human articular cartilage. The suppressive effects of LPS on cartilage biosynthetic activity are dependent on the presence of TLR-4, are governed, at least in part, by an up-regulation of IL-1beta, and are mediated by p38 kinase. These in vitro data indicate an anti-anabolic effect of TLR-4 in articular chondrocytes that may hamper cartilage repair in various joint diseases.

Accumulation of LPS by polyethylene particles decreases bone attachment to implants

Molecules absorbed on the surface of particulate wear debris may contribute to inflammatory reactions that lead to aseptic loosening of implants. Lipopolysaccharide (LPS), a bacterial endotoxin, can attach to many biomaterials and stimulate macrophages to secrete osteoclast-activating cytokines. We tested the adsorption of LPS by polyethylene particles in vitro and examined the biological effects of LPS absorption on bone remodeling around implants in vivo. Polyethylene particles were incubated in radiolabeled LPS solutions, and adsorption of LPS by the particles was quantified by radioassay. Because polyethylene particles are hydrophobic and less dense than water, they floated and clumped when incubated in a water solution of LPS, resulting in low adsorption of LPS. However, when particles were incubated in an ethanol solution of LPS, most of the LPS was adsorbed by the particles, and was resistant to washing with water. Triton X-100 (10%), however, effectively washed the LPS off the particles. In a rat model, the presence of polyethylene particles around the implant in the femoral canal decreased bone attachment to the implant at 6 weeks. Incubating the particles with LPS before implantation, or intermittent administration of LPS systemically, further decreased bone-implant attachment to similar extents, but had no effect on the bone density of the control side femurs. Our data indicate that polyethylene particles have high affinity for LPS, depending on many factors, especially the solvents of the LPS. Intermittent systemic administration of LPS affects bone remodeling but only occurs in the area containing polyethylene particles and titanium implants, supporting the hypothesis that the presence of polyethylene particles around implants can result in accumulation of LPS from exogenous sources. This may cause local levels of LPS that are high enough to affect bone remodeling around implants.

Lipopolysaccharide impairs fracture healing: an experimental study in rats

BACKGROUND

It has been shown that trauma causes translocation of lipopolysaccharide (LPS) endotoxins from the gut. LPS has been identified as a major bacterial bone resorbing factor. The effects of LPS on bone healing are therefore of clinical interest, as trauma involving fractures followed by sepsis is a clinical scenario. We investigated the effects of systemic and local administration of LPS on the healing of femoral fractures in rats.

ANIMALS AND METHODS

In 3 groups, each consisting of 9 rats, a mid-diaphyseal osteotomy/fracture of the femoral bone was performed and then nailed. In one group of animals, LPS was applied intraperitoneally (systemically), and in another group, LPS was applied locally at the fracture site. The third group served as a control. The animals were killed after 6 weeks, and the mechanical characteristics of the healing osteotomies were evaluated.

RESULTS

We found that LPS induced a hypertrophic and immature callus, as evaluated by bone mineral content and density. In the rats given LPS intraperitoneally, the mechanical strength characteristics were reduced, as evaluated by bending moment, rigidity, and energy absorption.

INTERPRETATION

The rats given LPS intraperitoneally reflect a clinical situation with fracture trauma and endotoxinemia. Our findings indicate that endotoxinemia may impair the fracture healing processes.

Xylitol inhibits inflammatory cytokine expression induced by lipopolysaccharide from Porphyromonas gingivalis

Porphyromonas gingivalis is one of the suspected periodontopathic bacteria. The lipopolysaccharide (LPS) of P. gingivalis is a key factor in the development of periodontitis. Inflammatory cytokines play important roles in the gingival tissue destruction that is a characteristic of periodontitis. Macrophages are prominent at chronic inflammatory sites and are considered to contribute to the pathogenesis of periodontitis. Xylitol stands out and is widely believed to possess anticaries properties. However, to date, little is known about the effect of xylitol on periodontitis. The aim of the present study was to determine tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) expression when RAW 264.7 cells were stimulated with P. gingivalis LPS (hereafter, LPS refers to P. gingivalis LPS unless stated otherwise) and the effect of xylitol on the LPS-induced TNF-alpha and IL-1beta expression. The kinetics of TNF-alpha and IL-1beta levels in culture supernatant after LPS treatment showed peak values at 1 h (TNF-alpha) and 2 to 4 h (IL-1beta), respectively. NF-kappaB, a transcription factor, was also activated by LPS treatment. These cytokine expressions and NF-kappaB activation were suppressed by pretreatment with pyrrolidine dithiocarbamate (an inhibitor of NF-kappaB). Pretreatment with xylitol inhibited LPS-induced TNF-alpha and IL-1beta gene expression and protein synthesis. LPS-induced mobilization of NF-kappaB was also inhibited by pretreatment with xylitol in a dose-dependent manner. Xylitol also showed inhibitory effect on the growth of P. gingivalis. Taken together, these findings suggest that xylitol may have good clinical effect not only for caries but also for periodontitis by its inhibitory effect on the LPS-induced inflammatory cytokine expression.

Porphyromonas gingivalis lipopolysaccharide antagonizes Escherichia coli lipopolysaccharide at toll-like receptor 4 in human endothelial cells

E. coli lipopolysaccharide (LPS) induces cytokine and adhesion molecule expression via the toll-like receptor 4 (TLR4) signaling complex in human endothelial cells. In the present study, we investigated the mechanism by which Porphyromonas gingivalis LPS antagonizes E. coli LPS-dependent activation of human endothelial cells. P. gingivalis LPS at 1 micro g/ml inhibited both E. coli LPS (10 ng/ml) and Mycobacterium tuberculosis heat shock protein (HSP) 60.1 (10 micro g/ml) stimulation of E-selectin mRNA expression in human umbilical vein endothelial cells (HUVEC) without inhibiting interleukin-1 beta (IL-1beta) stimulation. P. gingivalis LPS (1 micro g/ml) also blocked both E. coli LPS-dependent and M. tuberculosis HSP60.1-dependent but not IL-1beta-dependent activation of NF-kappaB in human microvascular endothelial (HMEC-1) cells, consistent with antagonism occurring upstream from the TLR/IL-1 receptor adaptor protein, MyD88. Surprisingly, P. gingivalis LPS weakly but significantly activated NF-kappaB in HMEC-1 cells in the absence of E. coli LPS, and the P. gingivalis LPS-dependent agonism was blocked by transient expression of a dominant negative murine TLR4. Pretreatment of HUVECs with P. gingivalis LPS did not influence the ability of E. coli LPS to stimulate E-selectin mRNA expression. Taken together, these data provide the first evidence that P. gingivalis LPS-dependent antagonism of E. coli LPS in human endothelial cells likely involves the ability of P. gingivalis LPS to directly compete with E. coli LPS at the TLR4 signaling complex.

Porphyromonas gingivalis lipopolysaccharide signaling in gingival fibroblasts-CD14 and Toll-like receptors

Periodontal disease is the major cause of adult tooth loss and is commonly characterized by a chronic inflammation caused by infection of oral bacteria. Porphyromonas gingivalis (P. gingivalis) is one of the suspected periodontopathic bacteria and is frequently isolated from the periodontal pockets of patients with chronic periodontal disease. The lipopolysaccharide (LPS) of P. gingivalis is a key factor in the development of periodontitis. Gingival fibroblasts, which are the major constituents of gingival connective tissue, may directly interact with bacteria and bacterial products, including LPS, in periodontitis lesions. It is suggested that gingival fibroblasts play an important role in the host responses to LPS in periodontal disease. P. gingivalis LPS enhances the production of inflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) in gingival fibroblasts. However, the receptor that binds with P. gingivalis LPS on gingival fibroblasts remained unknown for many years. Recently, it was demonstrated that P. gingivalis LPS binds to gingival fibroblasts. It was also found that gingival fibroblasts express CD14, Toll-like receptor 4 (TLR4), and myeloid differentiation primary response gene 88 (MyD88). P. gingivalis LPS treatment of gingival fibroblasts activates several intracellular proteins, including protein tyrosine kinases, and up-regulates the expression of monocyte chemoattractant protein-1 (MCP-1), extracellular signal-regulated kinase 1 (ERK1), and signal-regulated kinase 2 (ERK2), IL-1 receptor-associated kinase (IRAK), nuclear factor-kappaB (NF-kappaB), and activating protein-1 (AP-1). These results suggest that the binding of P. gingivalis LPS to CD14 and TLR4 on gingival fibroblasts activates various second-messenger systems. In this article, we review recent findings on the signaling pathways induced by the binding of P. gingivalis LPS to CD14 and Toll-like receptors (TLRs) in gingival fibroblasts.

Primary role of interleukin-1 alpha and interleukin-1 beta in lipopolysaccharide-induced hypoglycemia in mice

Within a few hours of its injection into mice, lipopolysaccharide (LPS) induces hypoglycemia and the production of various cytokines. We previously found that interleukin-1 alpha (IL-1 alpha), IL-1 beta, and tumor necrosis factor alpha (TNF-alpha) induce hypoglycemia and that the minimum effective dose of IL-1 alpha or IL-1 beta is about 1/1000 that of TNF-alpha. In the present study, we examined the contribution made by IL-1 to the hypoglycemic action of LPS. Nine other cytokines tested were all inactive at inducing hypoglycemia. LPS produced hypoglycemia in mice deficient in either IL-1 alpha or IL-1 beta but not in mice deficient in both cytokines (IL-1 alpha and -1 beta knockout [IL-1 alpha/beta KO] mice). IL-1 alpha, IL-1 beta, and TNF-alpha induced hypoglycemia in IL-1 alpha/beta KO mice, as they did in normal control mice. The LPS-induced elevation of serum cortisol was weaker in IL-1 alpha/beta KO mice than in control mice, and, in the latter, serum cortisol was markedly raised while blood glucose was declining. IL-1 alpha decreased blood glucose both in NOD mice (which have impaired insulin production) and in KK-Ay mice (insulin resistant). These results suggest that (i). cortisol may not be involved in mediating the resistance of IL-1 alpha/beta KO mice to the hypoglycemic action of LPS, (ii). as a mediator, IL-1 is a prerequisite for the hypoglycemic action of LPS, (iii). IL-1 alpha and IL-1 beta perform mutual compensation, and (iv). IL-1 plays a role as the primary stimulator of the many anabolic reactions required for the elaboration of immune responses against infection.

The role of adsorbed endotoxin in particle-induced stimulation of cytokine release

Numerous in vitro models have demonstrated the capacity of wear particles to stimulate the release of soluble pro-inflammatory products with the ability to induce local bone resorption. Recent observations have demonstrated that binding of lipopolysaccharide (LPS) to particulate wear debris can significantly modulate the pattern of cell response in the in vitro models. These findings raise concerns over the possible role of LPS in the pathogenesis of aseptic loosening after total joint replacements, and also indicates the importance of controlling for possible confounding effects of LPS contamination in the in vitro models used to study the reactive nature of wear debris. Our studies were undertaken to rigorously analyze the effects of particle-associated LPS on cell responses and to assess the efficacy of different treatment protocols to inactivate LPS associated with different particulate materials. Particles of cobalt-chrome alloy, titanium-6-aluminum-4-vanadium, titanium nitride and silica were pretreated with LPS and exposed to multiple treatment protocols. When cells were treated with "as-received" particles prepared by washing in ethanol, small amounts of TNF-alpha, IL-1beta. and IL-1alpha were detected. In contrast, all particle species pretreated with LPS produced marked increases in TNF-alpha, IL-1alpha, and IL-1beta release, as well as upregulation of corresponding mRNA levels even after ethanol washing. Boiling the LPS-pretreated particles in 1% acetic acid or autoclaving and baking the particles also markedly reduced and in some instances abolished the effect of the LPS-pretreatment. This indicates that LPS binds to the surface of particles of diverse composition and that the bound LPS is biologically active. Treatment protocols to inactivate particle-associated LPS demonstrated significant differences in efficacy. When the most rigorous treatments were utilized, essentially all LPS activity could be eliminated. Particles treated with these methods retained some capacity to stimulate cytokine release, but activities were markedly reduced. These results provide further evidence indicating that LPS contamination of particulate materials can markedly enhance their biological activity. This potential confounding effect needs to be carefully monitored and controlled in the in vitro model systems used to evaluate wear particles. Furthermore, the presence of particle-associated endotoxin at the bone-implant interface in vivo could markedly enhance the adverse biological activity of particulate wear debris.

Contribution of interleukin-11 and prostaglandin(s) in lipopolysaccharide-induced bone resorption in vivo

We previously demonstrated that interleukin-1 (IL-1) and tumor necrosis factor (TNF) activities only partially account for calvarial bone resorption induced by local application of lipopolysaccharide (LPS) in mice. The present study was undertaken to determine the role and relative contribution of IL-11 and prostaglandin(s) (PG[s]) in LPS-induced bone resorption in vivo. A one-time dose of LPS was injected into the subcutaneous tissue overlying calvaria of mice lacking IL-1 receptor type I (IL-1RI(-/-)), mice lacking TNF receptor p55 and IL-1RI (TNFRp55(-/-)-IL-1RI(-/-)), and wild-type mice. Mice were then treated with injections of anti-IL-11 monoclonal antibody (MAb), indomethacin, or phosphate-buffered saline (PBS) and sacrificed 5 days later. Histological sections stained for tartrate-resistant acid phosphatase (TRAP) were quantified by histomorphometric analysis. At low doses of LPS (100 microg/mouse), the percentages of bone surface covered by osteoclasts were found to be similar in three strains of mice. The increase was reduced by 37% with anti-IL-11 MAb and by 46% with indomethacin. At higher doses of LPS (500 microg/mouse), we found an eightfold increase in these percentages in wild-type mice and a fivefold increase in these percentages in IL-1RI(-/-) and TNFRp55(-/-)-IL-1RI(-/-) mice after normalizing with the value from the saline-PBS control group in the same strain of mice. The increase was reduced by 55 and 69% in wild-type mice and by 50 and 57% in IL-1RI(-/-) and TNFRp55(-/-)-IL-1RI(-/-) mice treated with anti-IL-11 MAb or indomethacin, respectively. Our findings suggest that in vivo, at low doses of LPS (100 microg/mouse), LPS-induced bone resorption is mediated by IL-11 and PGs, while at high doses of LPS (500 microg/mouse), it is mediated by IL-11, PGs, IL-1, and TNF signaling. IL-11 and PGs mediate LPS-induced bone resorption by enhancing osteoclastogenesis independently of the IL-1 or TNF signaling.

Effect of anti-CD14 antibody on experimental periodontitis induced by Porphyromonas gingivalis lipopolysaccharide

The lipopolysaccharide (LPS) released by Porphyromonas gingivalis, a Gram-negative bacterium found in the periodontal pockets of patients with periodontitis, induces bone resorbing activity in vivo. We previously showed that a receptor for LPS on human gingival fibroblasts and gingival epithelial cells is CD14. In this study, we established a mouse model of experimental periodontitis by applying a P. gingivalis LPS solution to the buccal region of mice. P. gingivalis LPS-induced bone resorption and interleukin-6 production in the gingival tissues were significantly inhibited by pretreatment with anti-CD14 antibody for 5 weeks prior to LPS treatment. This result suggests that anti-CD14 antibody may be usable as a prototype for the development of drugs for the treatment of periodontal disease.

The carboxyl-terminal domain of closely related endotoxin-binding proteins determines the target of protein-lipopolysaccharide complexes

The bactericidal/permeability increasing (BPI) and lipopolysaccharide (LPS)-binding (LBP) proteins are closely related two-domain proteins in which LPS binding is mediated by the NH(2)-terminal domain. To further define the role of the COOH-terminal domain of these proteins in delivery of LPS to specific host acceptors, we have compared interactions of LBP, BPI, LBP(N)-BPI(C) (NH(2)-terminal domain of LBP, COOH-terminal domain of BPI), and BPI(N)-LBP(C) with purified (3)H-LPS and, subsequently, with purified leukocytes and soluble (s)CD14. The COOH-terminal domain of LBP promotes delivery of LPS to CD14 on both polymorphonuclear leukocytes and monocytes resulting in cell activation. In the presence of Ca(2+) and Mg(2+), LBP and BPI each promote aggregation of LPS to protein-LPS aggregates of increased size (apparent M(r) > 20 x 10(6) Da), but only LPS associated with LBP and BPI(N)-LBP(C) is disaggregated in the presence of CD14. BPI and LBP(N)-BPI(C) promote apparently CD14-independent LPS association to monocytes without cell activation. These findings demonstrate that the carboxyl-terminal domain of these closely related endotoxin-binding proteins dictates the route and host responses to complexes they form with endotoxin.

Salivary antioxidants and periodontal disease status

Periodontal disease is a common chronic adult condition. The bacterium Porphyromonas gingivalis has been implicated in the aetiology of this disease, which causes destruction of the connective tissue and bone around the root area of the tooth. It has been observed that invading P. gingivalis bacteria trigger the release of cytokines such as interleukin 8 and tumour necrosis factor a, leading to elevated numbers and activity of polymorphonucleocytes (PMN). As a result of stimulation by bacterial antigens, PMN produce the reactive oxygen species (ROS) superoxide via the respiratory burst as part of the host response to infection. Patients with periodontal disease display increased PMN number and activity. It has been suggested that this proliferation results in a high degree of ROS release, culminating in heightened oxidative damage to gingival tissue, periodontal ligament and alveolar bone. Antioxidant constituents in plasma have been well-documented, being chiefly ascorbate, albumin and urate, and these are known to display sensitivity to dietary antioxidant intakes. The concentration of antioxidants in saliva does not appear to mirror those of plasma. The extent of dietary influence upon salivary antioxidant status is unclear. Urate is the predominant salivary antioxidant, with albumin and ascorbate providing minor contributions. Previous research has found reduced salivary antioxidant activity in patients suffering from periodontal disease. An improved understanding of the role antioxidants play in periodontitis, and the influence of nutrition on antioxidant status, may lead to a possible nutritional strategy for the treatment of periodontal disease.

Flow-cytometric analysis of lymphocyte subsets and mCD14 expression in patients with various periodontitis categories

BACKGROUND

Membrane-bound CD14 (mCD14) is expressed mainly on circulating monocytes and tissue macrophages. It is one of the receptors, which act at the recognition of lipopolysaccharides by host cells. Periodontopathic bacteria result in activation of cellular and humoral immune responses.

AIM

The aim of the present study was to analyze the peripheral blood mCD14 concentrations as well as cell surface markers of lymphocyte subsets in periodontitis patients of various categories.

MATERIALS AND METHODS

Peripheral blood samples were obtained from 22 early onset periodontitis (EOP), 10 adult periodontitis (AP) patients and 13 systemically and periodontally healthy control subjects. Three-color flow cytometry and a panel of relevant monoclonal antibodies were used to determine the percent expression of various cell surface markers on peripheral blood mononuclear cells (PBMCs). The results were tested statistically by one-way variance analysis and Newman Keuls test.

RESULTS

No significant difference was observed between the study groups with regard to the relative counts of B-cells, T-cells, T-helper, T-cytotoxic/suppressor, activated T-cells and natural killer cells. EOP patients expressed significantly lower level of interleukin-2 receptor (IL-2R) when compared with AP patients (6.08% and 19.3% respectively) (p<0.05). The level of mCD14 in EOP patients (7.18%) was lower than that of AP patients (9.3%) and the control subjects (9.2%), but the differences were not statistically significant.

CONCLUSIONS

The low level of IL-2R in the EOP group may be interpreted as an insufficient responsiveness to the periodontopathogens, which may be ultimately related with the more severe tissue destruction. Though not significant, the reduced expression of mCD14 in EOP group may also be related with the immune system deficiencies in these patients.

Heterogeneous expression of Toll-like receptor 4 and downregulation of Toll-like receptor 4 expression on human gingival fibroblasts by Porphyromonas gingivalis lipopolysaccharide

Porphyromonas gingivalis (P. gingivalis) is implicated in the initiation and progression of periodontitis. Human gingival fibroblasts (HGFs) are the major constituent of gingival connective tissue. P. gingivalis or its components such as lipopolysaccharide (LPS) upregulate the production of various inflammatory cytokines including interleukin (IL)-1 and IL-6 in HGFs. Recently, we demonstrated that the binding of P. gingivalis LPS to Toll-like receptor 4 (TLR4) on HGFs activates various second messenger systems (Biochem. Biophys. Res. Commun. 273, 1161-1167, 2000). In the present study, we examined the level of TLR4 expression on HGFs by flow cytometric analysis (FACS), and studied the levels of IL-1 and IL-6 in the culture medium upon LPS stimulation of HGFs by enzyme-linked immunosorbent assay (ELISA). Upon stimulation by P. gingivalis LPS for 24 h, HGFs that expressed a high level of TLR4 secreted significantly higher levels of IL-1 and IL-6 than HGFs that expressed a low level of TLR4. On the other hand, after stimulation with P. gingivalis LPS for 24 h, the level of TLR4 on the surface of HGFs decreased. These results suggest that the level of TLR4 expression on HGFs reflects the extent of inflammation in the gingival tissue, and that P. gingivalis LPS downregulates TLR4 expression on HGFs. These findings may be used to control inflammatory and immune responses in periodontal disease.

Differential mRNA expression of prostaglandin receptor subtypes in macrophage activation

Assessing the regulation of macrophage receptors for prostaglandin (PGE2) is essential to understanding the control which that potent lipid mediator has in modulating macrophage activities. The purpose of this study was to assess the differential mRNA expression of PGE2 receptor subtypes (EP) during macrophage exposure to activating and transducing agents. RAW 264.7 macrophages constitutively expressed mRNA for EP2,EP3 and EP4 receptor subtypes. Messenger RNA for EP4 was expressed at a much higher level when compared to EP2 in unstimulated macrophages as assessed by kinetic quantitative RT-PCR. When macrophages were stimulated with LPS, EP2 m RNA levels were 12-fold higher when compared to unstimulated macrophages, while EP4 m RNA remained unchanged. Conversely, mRNA levels of both EP2 and EP4 receptors were lower after macrophages were treated with IFN-gamma. Messenger RNA levels of both receptors were lower in macrophages after treatment with PGE2 or dibutyryl (db) cAMP Addition of the PKA inhibitor H89 reversed the effects of PGE2 and dbcAMP to varying degrees. Proteosome and p38 MAP kinase inhibitors blocked the LPS-stimulated increase in EP2 mRNA levels. Those inhibitors had no effect on EP4 mRNA.Thus, activating agents such as LPS and IFN-gamma may differentially regulate mRNAfor PGE2 receptor types in macrophages but the ligand and its associated signal transducing factors probably have similar regulatory effects.

Construction of acetate auxotrophs of Neisseria meningitidis to study host-meningococcal endotoxin interactions

To facilitate studies of the molecular determinants of host-meningococcal lipooligosaccharide (endotoxin) interactions at patho-physiologically relevant endotoxin concentrations (i.e. < or =10 ng/ml), we have generated acetate auxotrophs NMBACE1 from encapsulated Neisseria meningitidis (serogroup B, strain NMB) and NMBACE2 from an isogenic bacterial mutant lacking the polysialic acid capsule. Growth of the auxotrophs in medium containing [(14)C]acetate yielded (14)C-lipooligosaccharides containing approximately 600 cpm/ng. Gel sieving resolved 14C-lipooligosaccharide-containing aggregates with an estimated molecular mass of > or =20 x 10(6) Da (peak A) and approximately 1 x 10(6) Da (peak B) from both strains. Lipooligosaccharides in peaks A and B had the same fatty acid composition and SDS-polyacrylamide gel electrophoresis profile. 14C-Labeled capsule copurified with (14)C-lipooligosaccharides in peak B from NMBACE1, whereas the other aggregates contained only 14C-lipooligosaccharide. For all aggregates, lipopolysaccharide-binding protein and soluble CD14-induced delivery of lipooligosaccharides to endothelial cells and cell activation correlated with disaggregation of lipooligosaccharides. These processes were inhibited by the presence of capsule but unaffected by the size of the aggregates. In contrast, endotoxin activation of cells containing membrane CD14 was unaffected by capsule but diminished when endotoxin was presented in larger aggregates. These findings demonstrate that the physical presentation of lipooligosaccharide, including possible interactions with capsule, affect the ability of meningococcal endotoxin to interact with and activate specific host targets.

Toll-like receptor 4-mediated signal pathway induced by Porphyromonas gingivalis lipopolysaccharide in human gingival fibroblasts

The lipopolysaccharide (LPS) secreted by Porphyromonas gingivalis is implicated in the initiation and progression of periodontitis. Human gingival fibroblasts (HGFs) are the major constituent of gingival connective tissue. In this study, we examined the expression of Toll-like receptor 4 (TLR4) on HGFs by flow cytometric analysis, and studied the signal transduction induced by LPS stimulation of HGFs by enzyme-linked immunosorbent assay, Western blotting, and immunoprecipitation. We show that LPS binds to HGFs, and that HGFs express TLR4 and myeloid differentiation primary response gene 88 (MyD88). P. gingivalis LPS-induced interleukin (IL)-1 production in HGFs was inhibited by anti-TLR4 antibody. P. gingivalis LPS treatment of HGFs activated several intracellular proteins including protein tyrosine kinases, and upregulated the expression of IL-1 receptor-associated kinase (IRAK), nuclear factor-kappaB (NF-kappaB), and activating protein-1 (AP-1), and these events were suppressed by anti-TLR4 monoclonal antibody. Our findings suggest that the binding of P. gingivalis LPS to TLR4 on HGFs activates various second messenger systems.

Periodontal disease and atherosclerotic cardiovascular disease: confounding effects or epiphenomenon?

Recent evidence suggests that periodontal disease may predispose to atherosclerotic cardiovascular disease. Data support mechanisms of host-derived local and systemic proinflammatory responses similar to atherosclerosis, consisting of monocytic-derived cytokines and other inflammatory mediators, which are induced by periodontal pathogens and its endotoxin, lipopolysaccharide. These mechanisms may contribute to the start of vascular endothelial dysfunction and further sequelae leading to atherosclerosis. Experimental evidence and biologic plausibility appear to support this proposal. However, clinical evidence from a MEDLINE search from January 1966-December 1999 proposed a weak or no correlation primarily due to confounding factors. The aim of care is to reduce vulnerable pathogens from the infected periodontium by standard treatment; however, new approaches appear promising. Increased awareness of a potential link among infective agents, immunoinflammatory processes, and atherosclerosis may clarify clinical implications.

Lipopolysaccharide activates matrix metalloproteinase-2 in endothelial cells through an NF-kappaB-dependent pathway

Vascular endothelial cells release proteinases that degrade the extracellular matrix, thus enabling cell migration during angiogenesis and vasculogenesis. Endothelial cells secrete mainly the proform of matrix metalloproteinase-2 (proMMP-2). In this report, we examined several growth factors, cytokines, and other molecules for activation of MMP-2 by human umbilical vein endothelial cells. Of these factors, we found that lipopolysaccharide (LPS) is the strongest activator of MMP-2. LPS induced MMP-2 activation in a time- and dose-dependent manner. While pretreatment with zinc chelators or nuclear factor kappaB (NF-kappaB) inhibitors suppressed LPS-induced MMP-2 activation, pretreatment with phosphatidylinositol 3'-kinase inhibitors had no effect. These results indicate that, in endothelial cells, LPS can directly enhance angiogenesis by inducing MMP-2 activation mediated through an NF-kappaB pathway.

Modulation of macrophage and microglial responses to axonal injury in the peripheral and central nervous systems

OBJECTIVE

After axonal injury, macrophages rapidly infiltrate and become activated in the mammalian peripheral nervous system (PNS) but not the central nervous system (CNS). We used the dorsal root pathway to study factors that modulate the response of macrophages to degenerating axons in both the PNS and the CNS.

METHODS

Lewis rats underwent transection of dorsal roots (Group 1), stab within the spinal cord (Group II), crush at the dorsal root entry zone (Group III), transection of dorsal roots combined with a CNS lesion (Group IV), or systemic administration of a known activator of macrophages, lipopolysaccharide, alone (Group V) or combined with transection of dorsal roots (Group VI). ED-1 antibody stained for macrophages and activated microglia at 7, 14, and 42 days postinjury.

RESULTS

At early time points, Group I demonstrated ED-1 cells in the PNS but not the CNS portion of the degenerating dorsal roots. Group II revealed ED-1 cells near the stab lesion. Group III demonstrated ED-1 cells adjacent to the dorsal root entry zone crush site. Group IV revealed ED-1 cells along both the PNS and the CNS portions of the degenerating dorsal roots when the CNS lesion was placed near the transected roots. Group V demonstrated few ED-1 cells in the PNS and the CNS, whereas Group VI revealed a marked ED-1 cellular response along both the PNS and the CNS portions of the transected dorsal roots.

CONCLUSION

Local CNS trauma and systemic administration of lipopolysaccharide can "prime" macrophages/microglia, resulting in an enhanced response to degenerating axons in the CNS. Such priming might prove useful in promoting axonal regeneration.

Modulation of endotoxin- and enterotoxin-induced cytokine release by in vivo treatment with beta-(1,6)-branched beta-(1,3)-glucan

Leukocytes activated by endotoxin or enterotoxins release proinflammatory cytokines, thereby contributing to the cascade of events leading to septic shock. In the present studies, we analyzed the effects of in vivo administration of a soluble immunomodulator, beta-(1,6)-branched beta-(1,3)-glucan (soluble beta-glucan), on toxin-stimulated cytokine production in monocytes and lymphocytes isolated from treated mice. In vitro stimulation of lymphocytes isolated from soluble beta-glucan-treated mice with lipopolysaccharide (LPS) resulted in enhanced production of interleukin-6 (IL-6) and suppressed production of tumor necrosis factor alpha (TNF-alpha), while stimulation of these cells with staphylococcal enterotoxin B (SEB) or toxic shock syndrome toxin 1 (TSST-1) resulted in enhanced production of gamma interferon (IFN-gamma) and suppressed production of IL-2 and TNF-alpha compared to that in cells isolated from untreated mice. In vitro stimulation of monocytes isolated from soluble beta-glucan-treated mice with LPS also resulted in suppressed TNF-alpha production, while stimulation of these cells with SEB or TSST-1 resulted in suppressed IL-6 and TNF-alpha production compared to that in cells isolated from untreated mice. Thus, the overall cytokine pattern of leukocytes from soluble beta-glucan-treated mice reflects suppressed production of proinflammatory cytokines, especially TNF-alpha. Taken together, our results suggest that treatment with soluble beta-glucan can modulate the induction cytokines during sepsis, resulting in an overall decrease in host mortality.

Cyclosporin A inhibits collagenase gene expression via AP-1 and JNK suppression in human gingival fibroblasts

A frequent side effect of cyclosporin A (CsA) administration is gingival overgrowth. Although the molecular mechanisms of CsA-induced gingival overgrowth are still unknown, it has been postulated that CsA acts on lipopolysaccharide (LPS) to induce fibroblastic activity, which results in an increase of the extracellular matrix. Here we provide evidence that CsA is able to affect signal transduction of LPS-induced collagenase expression in fibroblasts. Treatment of fibroblasts with LPS caused activation of collagenase gene, activator protein-1 (AP-1) and c-Jun N-terminal kinase (JNK). These activations were blocked by CsA. We suggest that inhibitory effects of CsA on LPS-induced signal transduction may contribute to the mechanism of CsA-induced gingival overgrowth.

Periodontal disease and diabetes mellitus: a two-way relationship

Severe periodontal disease often coexists with severe diabetes mellitus. Diabetes is a risk factor for severe periodontal disease. A model is presented whereby severe periodontal disease increases the severity of diabetes mellitus and complicates metabolic control. We propose that an infection-mediated upregulation cycle of cytokine synthesis and secretion by chronic stimulus from lipopolysaccharide (LPS) and products of periodontopathic organisms may amplify the magnitude of the advanced glycation end product (AGE)-mediated cytokine response operative in diabetes mellitus. In this model, the combination of these 2 pathways, infection and AGE-mediated cytokine upregulation, helps explain the increase in tissue destruction seen in diabetic periodontitis, and how periodontal infection may complicate the severity of diabetes and the degree of metabolic control, resulting in a 2-way relationship between diabetes mellitus and periodontal disease/infection. This proposed dual pathway of tissue destruction suggests that control of chronic periodontal infection is essential for achieving long-term control of diabetes mellitus. Evidence is presented to support the hypothesis that elimination of periodontal infection by using systemic antibiotics improves metabolic control of diabetes, defined by reduction in glycated hemoglobin or reduction in insulin requirements.

Periodontal diseases' contributions to cardiovascular disease: an overview of potential mechanisms

Periodontitis and atherosclerosis have complex etiologies, genetic and gender predispositions, and potentially share many risk factors-the most significant of which may be smoking status. These diseases also have many pathogenic mechanisms in common. It is becoming increasingly clear that infections and chronic inflammatory conditions such as periodontitis may influence the atherosclerotic process. The severity and chronicity of periodontal disease provides a rich source of subgingival microbial and host response products and effects over a long time period. The objective of this review is to consider the mechanisms whereby diseases such as periodontitis, which is chronic and Inflammatory In nature and initiated by microbial plaque, can predispose to atherosclerosis. In common with periodontal disease. the pathogenesis of atherosclerosis is not completely understood and both diseases are currently under Intensive investigation. Two main processes in particular are worthy of consideration and may provide the link between these 2 diseases, namely the lipopolysaccharide-related responses and the hyperresponsive monocyte phenomenon. Insufficient experimental evidence exists, however, to further support these hypotheses at present and clearly more research is needed on both of these processes and the interrelationships between both diseases.