Expression of the endothelial leukocyte adhesion molecule-1 (ELAM-1) on endothelial cells in experimental gingivitis in humans

Maintaining a protective state for human periodontal tissue

Periodontitis, caused by infection with periodontal pathogens, is primarily characterized by inflammatory bone resorption and destruction of connective tissue. Simply describing periodontitis as a specific bacterial infection cannot completely explain the various periodontal tissue destruction patterns observed. Periodontal tissue damage is thought to be caused by various factors. In recent years, research goals for periodontal pathogens have shifted from searching for specific pathogens to investigating mechanisms that damage periodontal tissues. Bacteria interact directly with the host in several ways, influencing expression and activity of molecules that evade host defenses, and destroying local tissues and inhibiting their repair. The host's innate and acquired immune systems are important defense mechanisms that protect periodontal tissues from attack and invasion of periodontal pathogens, thus preventing infection. Innate and acquired immunity have evolved to confront the microbial challenge, forming a seamless defense network in periodontal tissues. In the innate immune response, host cells quickly detect, via specialized receptors, macromolecules and nucleic acids present on bacterial cell walls, and this triggers a protective, inflammatory response. The work of this subsystem of host immunity is performed mainly by phagocytes, beta-defensin, and the complement system. In addition, the first line of defense in oral innate immunity is the junctional epithelium, which acts as a physical barrier to the entry of oral bacteria and other nonself substances. In the presence of a normal flora, junctional epithelial cells differentiate actively and proliferate apically, with concomitant increase in chemotactic factor expression recruiting neutrophils. These immune cells play an important role in maintaining homeostasis and the protective state in periodontal tissue because they eliminate unwanted bacteria over time. Previous studies indicate a mechanism for attracting immune cells to periodontal tissue with the purpose of maintaining a protective state; although this mechanism can function without bacteria, it is enhanced by the normal flora. A better understanding of the relationship between the protective state and its disruption in periodontal disease could lead to the development of new treatment strategies for periodontal disease.

Polymeric Carriers for Delivery Systems in the Treatment of Chronic Periodontal Disease

Periodontitis (PD) is a chronic inflammatory disease of periodontal tissues caused by pathogenic microorganisms and characterized by disruption of the tooth-supporting structures. Conventional drug administration pathways in periodontal disease treatment have many drawbacks such as poor biodistribution, low selectivity of the therapeutic effect, burst release of the drug, and damage to healthy cells. To overcome this limitation, controlled drug delivery systems have been developed as a potential method to address oral infectious disease ailments. The use of drug delivery devices proves to be an excellent auxiliary method in improving the quality and effectiveness in periodontitis treatment, which includes inaccessible periodontal pockets. This review explores the current state of knowledge regarding the applications of various polymer-based delivery systems such as hydrogels, liposomes, micro-, and nanoparticles in the treatment of chronic periodontal disease. Furthermore, to present a more comprehensive understanding of the difficulties concerning the treatment of PD, a brief description of the mechanism and development of the disease is outlined.

Site-Specific Neutrophil Migration and CXCL2 Expression in Periodontal Tissue

The oral microbial community is the best-characterized bacterial ecosystem in the human host. It has been shown in the mouse that oral commensal bacteria significantly contribute to clinically healthy periodontal homeostasis by influencing the number of neutrophils that migrate from the vasculature to the junctional epithelium. Furthermore, in clinically healthy tissue, the neutrophil response to oral commensal bacteria is associated with the select expression of the neutrophil chemokine CXCL2 but not CXCL1. This preliminary study examined the contribution of commensal bacteria on neutrophil location across the tooth/gingival interface. Tissue sections from the root associated mesial (anterior) of the second molar to the root associated distal (posterior) of the second molar were examined for neutrophils and the expression of the neutrophil chemokine ligands CXCL1 and CXCL2. It was found that both the number of neutrophils as well as the expression of CXCL2 but not CXCL1 was significantly increased in tissue sections close to the interdental region, consistent with the notion of select tissue expression patterns for neutrophil chemokine expression and subsequent neutrophil location. Furthermore, mice gavaged with either oral Streptococcus or Lactobacillus sp. bacteria induced a location pattern of neutrophils and CXCL2 expression similar to the normal oral flora. These data indicate for the first time select neutrophil location and chemokine expression patterns associated with clinically healthy tissue. The results reveal an increased inflammatory load upon approaching the interproximal region, which is consistent with the observation that the interproximal region often reveals early clinical signs of periodontal disease.

Historical and contemporary hypotheses on the development of oral diseases: are we there yet?

Dental plaque is an oral biofilm that much like the rest of our microbiome has a role in health and disease. Specifically, it is the cause of very common oral diseases such as caries, gingivitis, and periodontitis. The ideas about oral disease development have evolved over time. In the nineteenth century, scientists could not identify bacteria related to disease due to the lack of technology. This led to the "Non-Specific Plaque Hypothesis" or the idea that the accumulation of dental plaque was responsible for oral disease without discriminating between the levels of virulence of bacteria. In the twentieth century this idea evolved with the techniques to analyze the changes from health to disease. The first common hypothesis was the "Specific Plaque Hypothesis" (1976) proposing that only a few species of the total microflora are actively involved in disease. Secondly, the "Non-Specific Plaque Hypothesis" was updated (1986) and the idea that the overall activity of the total microflora could lead to disease, was enriched by taking into account difference in virulence among bacteria. Then, a hypothesis was considered that combines key concepts of the earlier two hypotheses: the "Ecological Plaque Hypothesis" (1994), which proposes that disease is the result of an imbalance in the microflora by ecological stress resulting in an enrichment of certain disease-related micro-organisms. Finally, the recent "Keystone-Pathogen Hypothesis" (2012) proposes that certain low-abundance microbial pathogens can cause inflammatory disease by interfering with the host immune system and remodeling the microbiota. In this comprehensive review, we describe how these different hypotheses, and the ideas around them, arose and test their current applicability to the understanding of the development of oral disease. Finally, we conclude that an all-encompassing ecological hypothesis explaining the shifts from health to disease is still lacking.

Defensins and LL-37: a review of function in the gingival epithelium

Antimicrobial peptides represent an important aspect of the innate defense system that contributes to the control of bacterial colonization and infection. As studies have progressed it has become clear that antimicrobial peptides manifest other functions in addition to their antimicrobial effects. These functions include chemotaxis of numerous types of host cells involved in both the innate and adaptive immune responses. In this review, the antimicrobial activity, the regulation and the contribution to host homeostasis of alpha-defensins and LL-37, as well as of beta-defensins, are discussed in the context of their specific tissue locations in the junctional epithelium and oral epithelium, respectively.

Commensal bacteria-dependent select expression of CXCL2 contributes to periodontal tissue homeostasis

The oral and intestinal host tissues both carry a heavy microbial burden. Although commensal bacteria contribute to healthy intestinal tissue structure and function, their contribution to oral health is poorly understood. A crucial component of periodontal health is the recruitment of neutrophils to periodontal tissue. To elucidate this process, gingival tissues of specific-pathogen-free and germ-free wild-type mice and CXCR2KO and MyD88KO mice were examined for quantitative analysis of neutrophils and CXCR2 chemoattractants (CXCL1, CXCL2). We show that the recruitment of neutrophils to the gingival tissue does not require commensal bacterial colonization but is entirely dependent on CXCR2 expression. Strikingly, however, commensal bacteria selectively upregulate the expression of CXCL2, but not CXCL1, in a MyD88-dependent way that correlates with increased neutrophil recruitment as compared with germ-free conditions. This is the first evidence that the selective use of chemokine receptor ligands contributes to neutrophil homing to healthy periodontal tissue.

Degranulated mast cells and TNF-α in oral lichen planus and oral lichenoid reactions diseases

Background:

The objective of this study was to assess mast cells and TNF-α in oral lichen planus (OLP) and oral lichenoid reactions (OLR) patients as diagnostic marker to the differential diagnosis of OLP and OLR diseases.

Materials and Methods:

In this cross-sectional study, samples were obtained from 30 OLP and 30 OLR patients, between June 2010 and March 2011 in Dental clinic of the University of Isfahan, Iran. Mast cells in the reticular layer of the lamina propria for samples were evaluated using toluidine blue method and immunohistochemical technique. The clinical relevant data taken into account were: demographical data, total number and degranulated mast cells, ratio of degranulated mast cells and TNF-α positive degranulated mast cells.

Results:

In OLP and OLR, the total mast cells were 21.2 ± 7.9 and 20.3 ± 6.8, degranulated mast cells were 15.5 ± 6.9 and 19.2 ± 6.9, ratio of degranulated mast cells to total mast cells were 0.716 ± 0.067 and 0.946 ± 0.081, and TNF-α positive degranulated mast cells were 13.6 ± 6.3 and 17.1 ± 6.04, respectively. There was no significant difference for the total mast cells. But degranulated mast cells, ratio of degranulated mast cells and TNF-α positive degranulated mast cells in OLR were significantly higher than OLP patients.

Conclusions:

Our results showed that the degranulated mast cells, ratio of degranulated mast cells and TNF-α in OLR was significantly more than OLP patients and these may be able to be used as diagnostic markers to the differential diagnosis of OLP and OLR.

Antimicrobial photodynamic therapy may promote periodontal healing through multiple mechanisms

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) as an adjunctive treatment in addition to scaling and root planing for the treatment of periodontitis has been shown to be clinically useful. Its beneficial effect is reported to be due to its potent bactericidal activity. However, aPDT treatment has the potential to inactivate bacterial and host factors that contribute to disease. In this report, we demonstrate that aPDT treatment can simultaneously kill Porphyromonas gingivalis and inactivate its virulence-associated protease. It also inactivates host destructive cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1 beta.

METHODS

We developed a 96-well-based bacterial killing and protease inactivation assay that determined aPDT bactericidal and protease inactivation from the same sample. A cytokine inactivation assay that measured E-selectin expression in response to TNF-alpha and IL-1 beta was developed to measure the ability of aPDT to inactivate cytokine function.

RESULTS

A single aPDT treatment in vitro potently inactivated protease activity and resulted in a 4-log(10) reduction in the viability of P. gingivalis. Dose and time-of-exposure experiments revealed that protease inactivation occurred at lower concentrations of photosensitizer and less time of light exposure. Also, aPDT treatment potently and functionally inactivated IL-1 beta and TNF-alpha.

CONCLUSIONS

aPDT treatment may augment periodontal treatment by increasing bacterial killing, inactivating bacterial virulence factors, and inactivating host cytokines that impair periodontal restoration. Therefore, aPDT treatment may provide a more favorable healing environment.

The oral microbial consortium's interaction with the periodontal innate defense system

The oral microbial consortium is the most characterized polymicrobial microbial community associated with the human host. Extensive sampling of both microbial and tissue samples has demonstrated that there is a strong association between the type of microbial community found in the gingival crevice and the status of innate host mediator expression. The strong clinical association between the microbial community and the innate host response in both clinically healthy and diseased tissue suggests that the oral consortium has a direct effect on periodontal tissue expression of innate defense mediators. A preliminary study in germ-free mice has demonstrated that the oral commensal consortium has direct effect on IL-1beta expression, indicating that this microbial community may contribute to the strong protective status of healthy gingival tissue. Likewise, the lipopolysaccharide composition and invasion characteristics of Porphyromonas gingivalis, an oral bacterium strongly associated with periodontitis, suggest that it may be a keystone member of the oral microbial community and facilitate a destructive change in the protective gingival innate host status.

Immune processes in periodontal disease: a review

The inflammatory and immune processes in periodontitis are complex and, although a great deal of information is available, many questions remain. Variation in human susceptibility to periodontitis has long been accepted, but the pathological basis of this is poorly understood. Similarly, we know little of the differences, if any, between the pathology of chronic and aggressive periodontitis. Genetics and environmental influences play a role in the susceptibility process, but if and how that translates through the immune and inflammatory processes to produce the plasma cell-dominated lesions seen in periodontitis remain to be elucidated. This review will focus on immunological aspects of the inflammatory changes seen in gingivitis and periodontitis, addressing both humoral and cellular responses to the microbial insult from dental plaque. A tendency for an individual or site to form an extensive plasma cell infiltrate may indicate an inability to defend against periodontopathogens and thus a predisposition to periodontitis. The issues to be considered include: 1) homing of immune and inflammatory cells to target tissues; 2) their local proliferation and synthetic activity; 3) the cytokine profile of the leukocytes; 4) the immunoglobulin subclasses of locally produced antibodies; 5) mucosal and systemic immune characteristics of the response; 6) the humoral immune response in periodontal health and disease states; and 7) the antigenic target of the immune response in periodontal lesions.

Functional implication of the hydrolysis of platelet endothelial cell adhesion molecule 1 (CD31) by gingipains of Porphyromonas gingivalis for the pathology of periodontal disease

Periodontitis is a response of highly vascularized tissues to the adjacent microflora of dental plaque. Progressive disease has been related to consortia of anaerobic bacteria, with the gram-negative organism Porphyromonas gingivalis particularly implicated. The gingipains, comprising a group of cysteine proteinases and associated hemagglutinin domains, are major virulence determinants of this organism. As vascular expression of leukocyte adhesion molecules is a critical determinant of tissue response to microbial challenge, the objective of this study was to determine the capacity of gingipains to modulate the expression and function of these receptors. Given the potential multifunctional role of platelet endothelial cell adhesion molecule 1 (PECAM-1) in the vasculature, the effect of gingipains on PECAM-1 expression by endothelial cells was examined. Activated gingipains preferentially down-regulated PECAM-1 expression on endothelial cells compared with vascular cell adhesion molecule 1 and endothelial-leukocyte adhesion molecule 1, but the reduction in PECAM-1 expression was completely inhibited in the presence of the cysteine proteinase inhibitor TLCK (Nalpha-p-tosyl-l-lysine chloromethyl ketone). Endothelial monolayers treated with activated gingipains demonstrated progressive intercellular gap formation that correlated with reduced intercellular junctional PECAM-1 expression as determined by Western blotting and immunofluorescence microscopy. This was accompanied by enhanced transfer of both albumin and neutrophils across the monolayer. The results suggest that degradation of PECAM-1 by gingipains contributes to increased vascular permeability and neutrophil flux at disease sites.

Porphyromonas gingivalis strain-dependent activation of human endothelial cells

Porphyromonas gingivalis is an important bacterium involved in periodontal diseases. Colonization by periodontopathogens has been associated with severe local inflammatory reactions in the connective tissue. In this study we characterized P. gingivalis-mediated infection and activation of human umbilical vein endothelial cells by using two strains of different virulence capacities, strains ATCC 53977 and DSMZ 20709. Both strains were able to adhere to and infect endothelial cells with an infection rate of 0.48% for ATCC 53977 and 0.007% for DSMZ 20709. The triggering of two signal transduction pathways in P. gingivalis-infected endothelial cells was demonstrated for both strains, with a rapid increase of p38 mitogen-activated protein kinase phosphorylation and a more delayed degradation of IkappaBalpha, followed by nuclear translocation of NF-kappaB. In addition, both strains induced enhanced expression of endothelial adhesion molecules E-selectin and intracellular adhesion molecule 1 (ICAM-1). Target cell activation was independent of bacterial fimbriae expression since the fimA knockout strain A7436 DeltafimA induced the same level of ICAM-1 as the corresponding wild type (A7436-WT). Thus, two P. gingivalis strains, ATCC 53799 and DSMZ 20709, infect endothelial cells and trigger signaling cascades leading to endothelial activation, which in turn may result in or promote severe local and systemic inflammation.

Expression of ICAM-1 and E-selectin in gingival tissues of smokers and non-smokers with periodontitis

BACKGROUND

Tobacco smoking affects systemic concentrations of soluble intercellular adhesion molecule (ICAM)-1, but its effect on local expression of adhesion molecules in gingival tissue has not been studied previously.

METHODS

E-selectin and ICAM-1 expression on small blood vessel endothelia in gingival biopsies obtained from smokers (n=17) and non-smokers (n=17) with periodontitis was examined with immunohistochemistry. Blood vessels were identified with monoclonal antibody for von Willebrand's factor.

RESULTS

A significantly larger number of vessels were observed in inflamed tissues of non-smokers than smokers (P<0.05). The number and proportion of vessels expressing both ICAM-1 and E-selectin was greater in sites with inflammation compared to non-inflamed sites in both smokers and non-smokers (P<0.05). The proportion of the total number of vessels expressing ICAM-1 in non-inflamed sites was greater in non-smokers compared with smokers (P<0.05).

CONCLUSIONS

These results suggest that the inflammatory response in smokers with periodontitis may not be accompanied by an equivalent increase in vascularity. Reduced ICAM-1 expression in non-inflamed areas of smokers could reflect a systemic effect of tobacco smoking on ICAM-1 independent of inflammation.

Adherence to and penetration through endothelial cells by oral treponemes

Oral spirochetes were co-incubated with monolayers of endothelial cells seeded into multiwell plates or onto filters mounted in plastic chambers. Attachment was assessed using an enzyme-linked immunosorbent assay and scanning electron microscopy. Invasiveness was determined by monitoring media beneath filters within chambers for spirochetes using darkfield microscopy. Transmission electron microscopy was used to estimate intercellular and intracellular passage of spirochetes through monolayers. All tested treponemes attached to monolayers in a dose- and time-dependent manner, except Treponema phagedenis. A few treponemes were observed within host cell cytoplasm. Unidentified spirochetes obtained from dental plaque were also invasive. Results indicate that oral spirochetes possess virulence-associated characteristics shared with pathogenic spirochetes. Further studies should examine the possibility that invasive spirochetes could disseminate from within affected gingiva.

Local chemokine paralysis, a novel pathogenic mechanism for Porphyromonas gingivalis

Periodontitis, which is widespread in the adult population, is a persistent bacterial infection associated with Porphyromonas gingivalis. Gingival epithelial cells are among the first cells encountered by both P. gingivalis and commensal oral bacteria. The chemokine interleukin 8 (IL-8), a potent chemoattractant and activator of polymorphonuclear leukocytes, was secreted by gingival epithelial cells in response to components of the normal oral flora. In contrast, P. gingivalis was found to strongly inhibit IL-8 accumulation from gingival epithelial cells. Inhibition was associated with a decrease in mRNA for IL-8. Antagonism of IL-8 accumulation did not occur in KB cells, an epithelial cell line that does not support high levels of intracellular invasion by P. gingivalis. Furthermore, a noninvasive mutant of P. gingivalis was unable to antagonize IL-8 accumulation. Invasion-dependent destruction of the gingival IL-8 chemokine gradient at sites of P. gingivalis colonization (local chemokine paralysis) will severely impair mucosal defense and represents a novel mechanism for bacterial colonization of host tissue.

Human gingival keratinocytes express E-selectin (CD62E)

OBJECTIVES

E-selectin (CD62E) is an adhesion molecule that participates in the binding of leukocytes to activated blood vascular endothelium. The present study was undertaken to characterise the pattern of E-selectin expression on epithelial cells of the gingival crevice and oral epithelium.

METHODS

A panel of six anti-E-selectin monoclonal antibodies was reacted with cryosections of human gingiva and cytospins of cultured gingival keratinocytes.

RESULTS

Three antibodies raised against leukocyte binding epitopes of the molecule (H4/18, H18/7, 1.2B6) were reactive with gingival keratinocytes, three were negative (4D10, BBA1, BBA2), while all six reacted with endothelial cells. Staining with H18/7 and 1.2B6 was weaker and more variable than with H4/18. In cell culture, levels of E-selectin expression reduced slowly, and were only modestly increased by treatment with exogenous TNF alpha, a known inducer of E-selectin on endothelium.

CONCLUSIONS

E-selectin epitopes are expressed on gingival keratinocytes. These binding epitopes may be involved in the traffic of leukocytes in this tissue compartment.

Differential reactivity of anti-E-selectin monoclonal antibodies in human gingival tissue

E-selectin is a cytokine-inducible endothelial glycoprotein which participates in the binding of leukocytes to vascular endothelium. Variable levels of expression of E-selectin have been reported in gingivitis and periodontitis, and two differing concepts of its significance have emerged: either gingival blood vessels express E-selectin constitutively, or are continuously activated by inflammatory mediators arising from the gingival environment. A range of monoclonal antibodies reacting with different epitopes of E-selectin are available commercially. The present study explored the possibility that the choice of antibody could affect estimation of the level of expression of E-selectin in vivo. Five monoclonal antibodies were used to investigate E-selectin expression in serial cryosections of human gingival tissue. While E-selectin-positive vascular endothelial cells were detected with all antibodies, the number of positively staining endothelial cells varied, with BBA1 > H4/18 = H18/7 = 4D10 > 1.2B6. The frequency of strong staining in tissue specimens was BBA1 > 4D10 > H4/18 = H18/7 > 1.2B6, while the frequency of weak staining showed the reverse trend. Additionally, with antibodies H18/7 and 1.2B6, 17 and 36% of the specimens were E-selectin negative. The occurrence of what appear to be false positives and false negatives confounds estimation of the level of E-selectin expression. Based on these findings, patterns of endothelial E-selectin expression in gingivitis and periodontitis should be re-evaluated.

ICAM-1-expressing pocket epithelium, LFA-1-expressing T cells in gingival tissue and gingival crevicular fluid as features characterizing inflammatory cell invasion and exudation in adult periodontitis

Activated T lymphocytes constitute a major component of inflammatory cells in the early periodontal lesion, and also appear in the gingival crevicular fluid. In an attempt to clarify the relationship between the ICAM-1 (CD54) expression of pocket epithelium in gingiva and the infiltrating lymphocyte population, we carried out an analysis of CD11a+(LFA-1 alpha), CD25+(IL-2R alpha) and CD4+(Th) cells subjacent to ICAM-1-expressing pocket epithelia and CD11a+CD25+CD4+ cells in gingival crevicular fluid (GCF). GCF was collected by crevicular washing from 16 patients with periodontitis (P group) and 3 subjects with healthy gingiva (H group). Peripheral blood (PB) was collected at the same time. Mononuclear cells were isolated by Ficoll-paque gradient centrifugation from GCF and PB. Monoclonal antibodies (mAb) to CD11a, CD25, and CD4 were used for three-color flow cytometry. Gingival biopsies were obtained from 7 patients in P group and 3 subjects in H group. Serial cryostat sections (6 microns in thickness) were prepared from each biopsy, on which a double staining was performed. The number of CD11a+CD25+CD4+ cells and the fluorescence intensity of FITC conjugated anti-CD11a were significantly higher in GCF than in PB (p < 0.001 to p < 0.01). CD11a+CD25+CD4+ cells were not detected in GCF in H group. The pocket epithelia expressed CD54 in P group, but not in H group. The number of CD11a+, CD25+ and CD4+ cells infiltrating the connective tissue subjacent to the upper, middle and lower parts of the CD54 positive pocket epithelium (n = 16) was 141 +/- 26, 38 +/- 13, 144 +/- 29 (cells/0.04 mm2), respectively, whereas in the CD54 negative pocket epithelium, it was (n = 5) 9 +/- 2, 3 +/- 1, 8 +/- 3. In P group, the CD11a+CD25+CD4+ cell number in GCF correlated with CD25+, CD11a+ cells in the connective tissue subjacent to the CD54+ pocket epithelium. These results indicate that expression of ICAM-1 in pocket epithelium is relevant to the migration of CD11a, CD25, CD4 positive cells in connective tissue subjacent to the pocket epithelium into the periodontal pocket. Assessing the relationship of our findings and other adhesion molecules would offer important clues to the understanding of T cell migration in affected gingiva.

Relationship between mast cell degranulation and inflammation in the oral cavity

Mast cells are granule-containing secretory cells which are distributed preferentially about the microvascular bed in oral mucosa. This work examined the contribution of mast cell mediators to inflammation in the oral cavity. Mast cells in oral tissues expressed the serine proteases, tryptase and chymase, with a minor subpopulation being chymase-negative. Mast cells contained the cytokine tumour necrosis factor-alpha (TNF) in their granules. Degranulation of mast cells was a consistent feature of inflammatory lesions (lichen planus, gingivitis, pulpitis, periapical inflammation). In lichen planus, intracellular stores of TNF were depleted, and expression of mRNA for TNF was upregulated, indicating ongoing production and release of the cytokine. The density of mast cells in tissue compartments was related to the level of expression of E-selectin, an endothelial adhesion molecule which is known to be induced in skin by TNF derived from degranulating mast cells. Further attention should be directed toward the role of mast cell products, particularly TNF, in inflammation in the oral cavity.

Ability of bacteria associated with chronic inflammatory disease to stimulate E-selectin expression and promote neutrophil adhesion

Porphyromonas gingivalis, Pseudomonas aeruginosa, and Helicobacter pylori have been shown to be associated with adult periodontal disease, chronic lung infections, and peptic ulcers, respectively. The ability of these bacteria to stimulate E-selectin expression and promote neutrophil adhesion, two components necessary for the recruitment of leukocytes in response to infection, was investigated. Little or no stimulation of E-selectin expression was observed with either P. gingivalis or H. pylori when whole cells, lipopolysaccharide (LPS), or cell wall preparations added to human umbilical cord vein endothelial cells were examined. P. aeruginosa was able to induce E-selectin to near-maximal levels; however, it required approximately 100 to 1,000 times more whole cells or LPS than that required by E. coli. Neutrophil-binding assays revealed that LPS and cell wall preparations obtained from these bacteria did not promote endothelial cell adhesiveness by E-selectin-independent mechanisms. In addition, P. gingivalis LPS blocked E-selectin expression by LPS obtained from other bacteria. We propose that lack of E-selectin stimulation and the inability to promote endothelial cell adhesiveness are two additional indications of low biologically reactive LPS. We suggest that this property of LPS may contribute to host tissue colonization. In addition, the ability of P. gingivalis to inhibit E-selectin expression may represent a new virulence factor for this organism.

Cell adhesion molecules in inflammation and immunity: relevance to periodontal diseases

Inflammatory and immune responses involve close contact between different populations of cells. These adhesive interactions mediate migration of cells to sites of inflammation and the effector functions of cells within the lesions. Recently, there has been significant progress in understanding the molecular basis of these intercellular contacts. Blocking interactions between cell adhesion molecules and their ligands has successfully suppressed inflammatory reactions in a variety of animal models in vivo. The role of the host response in periodontal disease is receiving renewed attention, but little is known of the function of cell adhesion molecules in these diseases. In this review we summarize the structure, distribution, and function of cell adhesion molecules involved in inflammatory/immune responses. The current knowledge of the distribution of cell adhesion molecules is described and the potential for modulation of cell adhesion molecule function is discussed.