High levels of soluble intercellular adhesion molecule-1 (ICAM-1) in crevicular fluid of periodontitis patients with plaque

Cannabinoid type-2 receptor agonist, inverse agonist, and anandamide regulation of inflammatory responses in IL-1β stimulated primary human periodontal ligament fibroblasts

OBJECTIVE

The aim of this study is to understand the role of cannabinoid type 2 receptor (CB2R) during periodontal inflammation and to identify anti-inflammatory agents for the development of drugs to treat periodontitis (PD).

BACKGROUND

Cannabinoid type 2 receptor is found in periodontal tissue at sites of inflammation/infection. Our previous study demonstrated anti-inflammatory responses in human periodontal ligament fibroblasts (hPDLFs) via CB2R ligands.

METHODS

Anandamide (AEA), HU-308 (agonist), and SMM-189 (inverse agonist) were tested for effects on IL-1β-stimulated cytokines, chemokines, and angiogenic and vascular markers expressed by hPDLFs using Mesoscale Discovery V-Plex Kits. Signal transduction pathways (p-c-Jun, p-ERK, p-p-38, p-JNK, p-CREB, and p-NF-kB) were investigated using Cisbio HTRF kits. ACTOne and Tango™ -BLA functional assays were used to measure cyclic AMP (cAMP) and β-arrestin activity.

RESULTS

IL-1β stimulated hPDLF production of 18/39 analytes, which were downregulated by the CB2R agonist and the inverse agonist. AEA exhibited pro-inflammatory and anti-inflammatory effects. IL-1β increased phosphoproteins within the first hour except p-JNK. CB2R ligands attenuated p-p38 and p-NFĸB, but a late rise in p-38 was seen with HU-308. As p-ERK levels declined, a significant increase in p-ERK was observed later in the time course by synthetic CB2R ligands. P-JNK was significantly affected by SMM-189 only, while p-CREB was elevated significantly by CB2R ligands at 180 minutes. HU-308 affected both cAMP and β-arrestin pathway. SMM-189 only stimulated cAMP.

CONCLUSION

The findings that CB2R agonist and inverse agonist may potentially regulate inflammation suggest that development of CB2R therapeutics could improve on current treatments for PD and other oral inflammatory pathologies.

Butyrate Decreases ICAM-1 Expression in Human Oral Squamous Cell Carcinoma Cells

Short-chain fatty acids (SCFA) are bacterial metabolites that can be found in periodontal pockets. The expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) within the epithelium pocket is considered to be a key event for the selective transmigration of leucocytes towards the gingival sulcus. However, the impact of SCFA on ICAM-1 expression by oral epithelial cells remains unclear. We therefore exposed the oral squamous carcinoma cell line HSC-2, primary oral epithelial cells and human gingival fibroblasts to SCFA, namely acetate, propionate and butyrate, and stimulated with known inducers of ICAM-1 such as interleukin-1-beta (IL1β) and tumor necrosis factor-alfa (TNFα). We report here that butyrate but not acetate or propionate significantly suppressed the cytokine-induced ICAM-1 expression in HSC-2 epithelial cells and primary epithelial cells. The G-protein coupled receptor-43 (GPR43/ FFAR2) agonist but not the histone deacetylase inhibitor, trichostatin A, mimicked the butyrate effects. Butyrate also attenuated the nuclear translocation of p65 into the nucleus on HSC-2 cells. The decrease of ICAM-1 was independent of Nrf2/HO-1 signaling and phosphorylation of JNK and p38. Nevertheless, butyrate could not reverse an ongoing cytokine-induced ICAM-1 expression in HSC-2 cells. Overall, these observations suggest that butyrate can attenuate cytokine-induced ICAM-1 expression in cells with epithelial origin.

Crevicular fluid levels of interleukin-8, interleukin-17 and soluble intercellular adhesion molecule-1 after regenerative periodontal therapy

Objective:

The aim of this study is to evaluate the influence of regenerative periodontal therapy on clinical parameters and interleukin-8 (IL-8), IL-17 and soluble intercellular adhesion molecule-1 (sICAM-1) levels in gingival crevicular fluid (GCF) of subjects with chronic periodontitis (CP).

Materials and Methods:

Fifteen patients received demineralized freeze-dried bone allograft (DFDBA) surgically to the site of infrabony defect. Clinical periodontal indices were recorded, and GCF samples were collected at baseline and at the 6^th and the 9^th month after the surgery.

Results:

Except plaque index, all clinical parameters improved following surgery (P < 0.05). The volume of GCF diminished from baseline to follow-up periods (P < 0.05). However, no effect was observed on the total amount of IL-8, IL-17 and sICAM-1 in GCF.

Conclusion:

DFDBA improved clinical outcome in CP subjects and was effective on decreasing the volume of GCF, but no effect was determined on IL-8, IL-17 and sICAM-1. Findings did not indicate a direct relationship between biochemical parameters and periodontal healing after demineralized freeze-dried bone grafting.

Local and systemic inflammatory responses to experimentally induced gingivitis

This study profiled the local and systemic inflammatory responses to experimentally induced gingivitis. Eight females participated in a 21-day experimental gingivitis model followed by a 14-day resolution phase. Bleeding on probing and plaque index scores were assessed before, during, and after resolution of gingival inflammation, and samples of saliva, GCF, and plasma were collected. Samples were assessed for biomarkers of inflammation using the BioPlex platform and ELISA. There were no significant changes in GCF levels of cytokines during the experimental phase; however, individual variability in cytokine profiles was noted. During resolution, mean GCF levels of IL-2, IL-6, and TNF-α decreased and were significantly lower than baseline levels (P = 0.003, P = 0.025, and P = 0.007, resp.). Furthermore, changes in GCF levels of IL-2, IL-6, and TNF-α during resolution correlated with changes in plaque index scores (r = 0.88, P = 0.004; r = 0.72, P = 0.042; r = 0.79, P = 0.019, resp.). Plasma levels of sICAM-1 increased significantly during the experimental phase (P = 0.002) and remained elevated and significantly higher than baseline levels during resolution (P < 0.001). These results support the concept that gingivitis adds to the systemic inflammatory burden of an individual.

Intracellular adhesion molecule-1 is regulated by porphyromonas gingivalis through nucleotide binding oligomerization domain-containing proteins 1 and 2 molecules in periodontal fibroblasts

BACKGROUND

The mechanism by which Porphyromonas gingivalis regulates intracellular adhesion molecule 1 (ICAM-1) expression in human periodontal ligament cells (hPDLCs) and human gingival fibroblasts (hGFs) is unknown. The aim of this study is to investigate whether nucleotide binding oligomerization domain-containing protein (NOD) 1 and NOD2 are involved in this process and the clinical significance of ICAM-1 in periodontitis.

METHODS

hPDLCs and hGFs were treated with P. gingivalis, l-Ala-γ-d-glutamyl-mesodiaminopimelic acid (an agonist for NOD1), and muramyl dipeptide (an agonist for NOD2). Alternatively, cells transfected with small interfering RNA targeting NOD1and NOD2 were treated with P. gingivalis. ICAM-1, NOD1, and NOD2 were detected at mRNA and protein levels. In addition, clinical examinations were performed in 30 healthy controls and 40 patients with chronic periodontitis (CP) before and after treatment, and serum-soluble ICAM-1 (sICAM-1) levels in these individuals were detected by enzyme-linked immunosorbent assay.

RESULTS

This study shows that P. gingivalis caused an increase in ICAM-1, NOD1, and NOD2 expression in periodontal fibroblasts. There was a linear correlation between ICAM-1 and NOD1 and NOD2 levels. Activation of NOD1 and NOD2 by the specific agonist led to the upregulation of ICAM-1, whereas knocking down NOD1 and NOD2 caused a reduction in P. gingivalis-induced ICAM-1 production. Furthermore, sICAM-1 levels were higher in patients with CP than in healthy controls and were positively related to the clinical periodontal parameters. After periodontal treatment, sICAM-1 levels decreased significantly.

CONCLUSIONS

The present results indicate that sICAM-1 levels are correlated to the severity of periodontitis. NOD1 and NOD2 mediate P. gingivalis-induced ICAM-1 production in periodontal fibroblasts. NOD1 and NOD2 could be considered potential targets for periodontal therapy.

Role of high endothelial postcapillary venules and selected adhesion molecules in periodontal diseases: a review

Periodontitis is accompanied by the proliferation of small blood vessels in the gingival lamina propria. Specialized postcapillary venules, termed periodontal high endothelial-like venules, are also present, and demonstrate morphological and functional traits similar to those of high endothelial venules (HEVs) in lymphatic organs. The suggested role of HEVs in the pathogenesis of chronic periodontitis involves participation in leukocyte transendothelial migration and therefore proinflammatory effects appear. Recent observations suggest that chronic periodontitis is an independent risk factor for systemic vascular disease and may result in stimulation of the synthesis of acute phase protein by cytokines released by periodontal high endothelial cells (HECs). However, tissue expression of HEV-linked adhesion molecules has not been evaluated in the gingiva of patients with chronic periodontitis. This is significant in relation to potential therapy targeting expression of the adhesion molecules. In this review, current knowledge of HEV structure and the related expression of four surface adhesion molecules of HECs [CD34, platelet endothelial cell adhesion molecule 1, endoglin and intercellular adhesion molecule 1 (ICAM-1)], involved in the key steps of the adhesion cascade in periodontal diseases, are discussed. Most studies on the expression of adhesion molecules in the development and progression of periodontal diseases pertain to ICAM-1 (CD54). Studies by the authors demonstrated quantitatively similar expression of three of four selected surface markers in gingival HEVs of patients with chronic periodontitis and in HEVs of reactive lymph nodes, confirming morphological and functional similarity of HEVs in pathologically altered tissues with those in lymphoid tissues.

Influence of periodontal therapy on the regulation of soluble cell adhesion molecule expression in aggressive periodontitis patients

BACKGROUND

Inflammatory periodontal disease is associated with an increased risk of cardiovascular disease. Circulating cell adhesion molecules (CAM) (intercellular adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1], and E-selectin) have been suggested as potential candidate markers of endothelial dysfunction, which contribute to the pathogenesis of cardiovascular diseases. The regulation of CAM in subjects with severe periodontitis and the influence of periodontal intervention on systemic CAM levels are not clear. The aim of this study was to determine whether intensive periodontal therapy reduces serum levels of CAM in patients with generalized aggressive periodontitis.

METHODS

Blood samples were collected at six treatment time points from 21 patients with previously untreated generalized aggressive periodontitis (mean age: 34.6 +/- 4.3 years). Patients received subgingival scaling and root planing and antibiotic therapy and were monitored over a 6-month recall period. Serum levels of soluble ICAM-1 (sICAM-1), VCAM-1 (sVCAM-1), and E-selectin (sE-selectin) were measured by enzyme-linked immunosorbent assay.

RESULTS

sE-selectin plasma levels decreased significantly (P <0.01) during periodontal therapy. Mean plasma levels were 65.95 ng/ml before treatment and 44.71 ng/ml 6 months after antibiotic therapy. sICAM-1 and sVCAM-2 serum levels were unaffected by therapeutic intervention.

CONCLUSIONS

Periodontal therapy reduces plasma sE-selectin levels. Whether this leads to a reduction in risk of future cardiovascular events in patients with aggressive periodontal disease warrants further studies.

No Association Between Selected Candidate Gene Polymorphisms and Severe Chronic Periodontitis

BACKGROUND

Chronic periodontitis (CP) risk is influenced by environmental and genetic factors. Using a case-control design, we tested for associations between CP and selected DNA sequence variations (single nucleotide polymorphisms [SNPs]) in or near genes coding for proteins that play a role in the pathogenesis of this disease.

METHODS

DNA was analyzed from 219 whites who were examined clinically. Cases (N=137) were >or=35 years of age with eight or more teeth having >or=5 mm of proximal clinical attachment loss. Controls (N=82) were >or=45 years of age with minimal or no proximal attachment loss or pocketing. Nine diallelic polymorphisms (gene and SNP descriptor) were studied in subjects: cytotoxic T-lymphocyte antigen-4 (CTLA-4, 49 A>G), human beta-defensin-1 (DEFB1, 692 G>A), intercellular adhesion molecule-1 (ICAM-1, 1548 A>G), Fas ligand (fasL, -844 C>T), inducible costimulator (ICOS, 3990 G>T), interleukin-6 (IL-6, -174 G>C), cysteine-cysteine chemokine receptor-5 (CCR5, 59653 C>T), osteoprotegerin (OPG, 245 T>G), and osteopontin (OPN, 707 C>T). Genotypes were determined using an automated fluorogenic 5'-nuclease, polymerase chain reaction-based assay. Gender and smoking history (pack-years) were included as covariates in logistic regression analyses.

RESULTS

Heavy smoking (>10 pack-years) and male gender were significantly associated with disease (P<0.001). For all SNPs tested, the allele frequencies and distributions of genotypes did not differ between cases and controls (P>0.05). No unadjusted or adjusted odds ratios (comparing genotypes in cases versus controls) were significantly different than 1.0 (P>0.05) under any additive, dominant, or recessive inheritance model.

CONCLUSIONS

None of the SNPs tested were strongly associated with generalized severe chronic periodontitis in North American whites. A potentially more fruitful approach in future studies will be to test for associations between periodontitis and haplotype blocks constructed from either multiple SNPs in candidate gene regions or from panels of markers that span the entire genome.

Detection and measurements of soluble intercellular adhesion molecules at implants and teeth: a comparative study

BACKGROUND

Adhesion molecules on endothelial cells and in the periodontal tissues control the immigration and retention of cells. The level of soluble intercellular adhesion molecules (sICAMs) has been used as a marker of the severity and/or extent of the inflammatory process in a wide range of pathologies, including periodontitis.

PURPOSE

This study was designed to detect and compare sICAM-1 at teeth and implants in relation to clinical periodontal and periimplant parameters.

METHOD

Regular recall patients with (1) implants and teeth, (2) implants, and (3) teeth were examined. Samples of sulcus fluid were collected from teeth and implants. The concentration of sICAM-1 was measured by enzyme-linked immunoabsorbent assay. Periodontal parameters were recorded after sampling.

RESULTS

The range of measured sICAM-1 was large (from below 100 to 1,200 ng/mL). The concentration of sICAM-1 was not different for teeth and implants but was significantly elevated in sites with positive bleeding on probing (BoP), namely, 571 ng/mL at teeth and 529 ng/mL at implants compared with 150 ng/mL and 169 ng/mL, respectively, with negative BoP. The regression analysis showed that the concentration of sICAM-1 was highly associated with positive BoP but was not dependent on the fluid volume.

CONCLUSIONS

A similarity of the sulcus fluid at teeth and implants was observed with regard to the detection of sICAM-1.

Changes in Soluble Adhesion Molecules in Gingival Crevicular Fluid Following Periodontal Surgery

BACKGROUND

Inflammation of periodontal tissues during postoperative wound healing is mediated by cell surface adhesion molecules. Soluble forms of these antigens have also been identified and shown to be important in immunoregulatory processes, but have previously not been investigated during periodontal repair and regeneration. The present study has examined the presence and possible changes in soluble intercellular adhesion molecule-1 (sICAM-1; CD54) and lymphocyte function-associated antigen-3 (sLFA-3; CD58) in gingival crevical fluid (GCF) following periodontal surgery.

METHODS

GCF samples were collected from four groups: 1) a guided tissue regeneration (GTR) test; 2) a GTR control, at least one complete tooth unit away from the periodontal defect; 3) a conventional flap (CF) surgery; and 4) a crown lengthening (CL). Sandwich enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of sICAM-1 and sLFA-3 in the GCF samples.

RESULTS

A marked increase in GCF volumes was found in all sites after surgery, although a persistent increase was associated only with the period of membrane retention at the GTR test sites. In addition, sICAM-1 and sLFA-3 were found in the GCF of healthy as well as diseased sites prior to treatment and the total amounts of both increased transiently following surgical intervention, especially sLFA-3. However, the concentrations of these GCF components, particularly sICAM-1, tended to decrease.

CONCLUSIONS

The temporal decrease in the concentration of sICAM-1 and sLFA-3 in GCF may serve to enhance inflammatory reactions at surgically-treated periodontal sites, thereby limiting repair and regeneration in the periodontium. These soluble adhesion molecules may thereby be of potential therapeutic value and might also be useful markers for monitoring periodontal wound healing.

Upregulation of intercellular adhesion molecule 1 and proinflammatory cytokines by the major surface proteins of Treponema maltophilum and Treponema lecithinolyticum, the phylogenetic group IV oral spirochetes associated with periodontitis and endodontic infections

Treponema maltophilum and Treponema lecithinolyticum belong to the group IV oral spirochetes and are associated with endodontic infections, as well as periodontitis. Recently, the genes encoding the major surface proteins (Msps) of these bacteria (MspA and MspTL, respectively) were cloned and sequenced. The amino acid sequences of these proteins showed significant similarity. In this study we analyzed the functional role of these homologous proteins in human monocytic THP-1 cells and primary cultured periodontal ligament (PDL) cells using recombinant proteins. The complete genes encoding MspA and MspTL without the signal sequence were cloned into Escherichia coli by using the expression vector pQE-30. Fusion proteins tagged with N-terminal hexahistidine (recombinant MspA [rMspA] and rMspTL) were obtained, and any possible contamination of the recombinant proteins with E. coli endotoxin was removed by using polymyxin B-agarose. Flow cytometry showed that rMspA and rMspTL upregulated the expression of intercellular adhesion molecule 1 (ICAM-1) in both THP-1 and PDL cells. Expression of proinflammatory cytokines, such as interleukin-6 (IL-6) and IL-8, was also induced significantly in both cell types by the Msps, as determined by reverse transcription-PCR and an enzyme-linked immunosorbent assay, whereas IL-1beta synthesis could be detected only in the THP-1 cells. The upregulation of ICAM-1, IL-6, and IL-8 was completely inhibited by pretreating the cells with an NF-kappaB activation inhibitor, l-1-tosylamido-2-phenylethyl chloromethyl ketone. This suggests involvement of NF-kappaB activation. The increased ICAM-1 and IL-8 expression in the THP-1 cells obtained with rMsps was not inhibited in the presence of the IL-1 receptor antagonist (IL-1ra), a natural inhibitor of IL-1. Our results show that the Msps of the group IV oral spirochetes may play an important role in amplifying the local immune response by continuous inflammatory cell recruitment and retention at an infection site by stimulation of expression of ICAM-1 and proinflammatory cytokines.

Mechanisms of action of environmental factors--tobacco smoking

AIM

To review the potential biological mechanisms underlying the effects of tobacco smoking on periodontitis.

MAIN FINDINGS

Smoking has major effects on the host response, but there are also a number of studies that show some microbiological differences between smokers and non-smokers. Smoking has a long-term chronic effect on many important aspects of the inflammatory and immune responses. Histological studies have shown alterations in the vasculature of the periodontal tissues in smokers. Smoking induces a significant systemic neutrophilia, but neutrophil transmigration across the periodontal microvasculature is impeded. The suppression of neutrophil cell spreading, chemokinesis, chemotaxis and phagocytosis have been described. Protease release from neutrophils may be an important mechanism in tissue destruction. Tobacco smoke has been found to affect both cell-mediated immunity and humoral immunity. Research on gingival crevicular fluid has demonstrated that there are lower levels of cytokines, enzymes and possibly polymorphonuclear cells in smokers. In vitro studies have shown detrimental effects of nicotine and some other tobacco compounds on fibroblast function, including fibroblast proliferation, adhesion to root surfaces and cytotoxicity.

CONCLUSION

Tobacco smoking has widespread systemic effects, many of which may provide mechanisms for the increased susceptibility to periodontitis and the poorer response to treatment.

Advances in periodontal disease markers

A computer-assisted medline search was conducted to find the relevant articles concerning the periodontal disease markers in gingival crevicular fluid (GCF) and saliva published during the 10-year period from 1993 to July 2003. This review suggests that certain diagnostic uses of saliva and GCF show promise. Although both fluids have been used to evaluate the risk for an individual to develop periodontal disease and to monitor of the host response to periodontal therapy, GCF has the chance of being closely approximated to the periodontal tissues where periodontal disease begins. The enzymes contributed to extracellular matrix (ECM) molecules and non-ECM molecules degradation and markers for polymorphonuclear leukocytes (PMN) activity and influx into the gingival tissue seem to provide valuable information regarding the periodontal disease diagnosis and prognosis. There is also an increasing evidence implicating reactive oxygen species and nitric oxide pathway in the pathogenesis of periodontal diseases. Although promising results have been achieved with the assays evaluating the markers in assessment of periodontal disease status, up to now, none of these tests are used routinely. Further, one commercially available genetic test has been reported to have the potential to be used to predict the periodontal disease, but there are controversial reports on this genetic susceptibility test.

N-acetyl-D-galactosamine specific lectin of Eikenella corrodens induces intercellular adhesion molecule-1 (ICAM-1) production by human oral epithelial cells

During the acute inflammatory response in periodontitis, gingival epithelial cells are considered to play important roles in the recruitment of inflammatory cells to the site of infection through the secretion of chemokines. However, little is known about the expression of molecules that are involved in the interaction between the epithelium and neutrophils following bacterial attachment. Earlier work reported that periodontopathogenic Eikenella corrodens strain 1,073 up-regulated the expression and secretion of chemokines such as interleukin-8 (IL-8) from KB cells (a human oral epithelial cell line derived from a human oral epidermoid carcinoma). To elucidate the mechanism of the transmigration of neutrophils through the epithelium, the present study investigated the expression of adhesion molecules on KB cells in response to E. corrodens attachment. Adhesion molecule gene expression was assessed by RT-PCR and adhesion proteins expressed on KB cell surfaces were determined by cell-based ELISA and FACS. In RT-PCR, ICAM-1 mRNA levels were significantly increased within 1 h in response to exposure to E. corrodens and continued to increase over the 12-h period of study. In ELISA, increased surface ICAM-1 expression was paralleled by increased ICAM-1 mRNA levels. Furthermore, the increases in ICAM-1 expression on epithelial cells infected with E. corrodens were observed to be due to the N-acetyl-D-galactosamine (GalNAc) specific bacterial lectin-like substance of E. corrodens (EcLS), which was one of the adhesins of E. corrodens. This is the first study to report that a bacterial lectin-like substance increased the expression of ICAM-1 on gingival epithelial cells.

Advantages of antisense drugs for the treatment of oral diseases

For almost two decades, antisense oligonucleotides (AS-ON) have been used successfully to suppress and regulate gene expression in vitro and in vivo. They are, meanwhile, well established to serve as molecular tools for several biologic applications, from the study of single gene functions up to complex target gene validations. Based on an at least theoretically simple mode of action, the sequence-specific inhibition of mRNA functions after complex formation by Watson-Crick base pairing and presumably enzymatic degradation of the target mRNA, they obviously carry a high therapeutic potential for the treatment of human diseases. In recent years, a remarkable number of clinical trials have been initiated and performed to evaluate the therapeutic usefulness of antisense technology. However, after the successful development of the first antisense-based drug Vitravene (Isis Pharmaceutical Inc., Carlsbad, CA) in 1998, no second product has appeared on the market to date. Here, we describe substantial advantages for the development of antisense-based drugs against less severe oral diseases that represent novel but highly promising application fields of the technology.

Antisense-mediated inhibition of ICAM-1 expression: a therapeutic strategy against inflammation of human periodontal tissue

Periodontal diseases, such as gingivitis and periodontitis, are caused by a mixed infection by several types of bacteria in the dental plaque, causing a chronic inflammation of the gingival mucosa. Inflammatory processes in conjunction with immune responses to bacterial attacks are generally protective. In profound periodontitis, however, hyperresponsiveness and hypersensitivity of the immune system are counterproductive because of the destruction of the affected periodontal connective tissues. The intercellular adhesion molecule type 1 (ICAM-1) plays a key role in the onset and manifestation of inflammatory responses. Thus, inhibition of ICAM-1 expression could be of therapeutic relevance for the treatment of destructive periodontitis. Here, antisense oligonucleotides (AS-ON) directed against ICAM-1 suppress protein expression and mRNA levels specifically and effectively in primary human endothelial cells of different tissue origin. Moreover, downregulation of ICAM-1 expression is also observed in AS-ON-transfected inflamed gingival mucosal tissue of patients with periodontal diseases. This work strongly suggests exploiting the local topical application of ICAM-1-directed AS-ON as a therapeutic tool against inflammatory processes of the human gingiva.

Interleukin-1beta regulation of adhesion molecules on human gingival and periodontal ligament fibroblasts

BACKGROUND

Adhesion molecules have been implicated in the pathogenesis of rheumatoid arthritis and may also play a role in the pathogenesis of periodontal disease by promoting the recruitment and retention of leukocytes in gingival tissue.

METHODS

The aim of the present study was to evaluate the capacity of interleukin-1beta (IL-1beta) to regulate adhesion molecule expression on clinically healthy human gingival (HGF) and periodontal ligament (PDL) fibroblasts. The HGF (n = 6) and PDL (n = 3) fibroblasts were treated with 1.0 ng/ml of IL-1beta for 24 hours and then incubated with primary intercellular adhesion molecule-1 (ICAM-1) and vascular cellular adhesion molecule-1 (VCAM-1) antibodies followed by FITC-conjugated secondary antibodies. The expression of ICAM-1 and VCAM-1 was measured by immunofluorescence flow cytometry.

RESULTS

The levels of ICAM-1 expression in IL-1beta treated HGF and PDL fibroblasts were statistically significant (P < or = 0.05) compared to normal untreated controls using log-transformed data and 3-way analysis of variance. Both cells expressed VCAM-1 after IL-1beta treatment, but the levels were not statistically different from controls.

CONCLUSIONS

This study demonstrated that IL-1beta upregulated ICAM-1 expression in both HGF and PDL fibroblasts. Even though the level of VCAM-1 was not statistically different from both HGF and PDL fibroblasts treated with IL-1beta compared to controls, both cells do express the VCAM-1 molecules. These results suggest that ICAM-1 and VCAM-1 might be involved in the pathogenesis of periodontal disease.

Cloning and characterization of a gene encoding an immunosuppressive factor from Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans is a pathogen of localized juvenile periodontitis and adult periodontitis. Immunomodulating activity is generally thought to be important in colonization by such pathogenic bacteria. Among the proteins possessing these activities, a 14 kDa immunosuppressive factor of A. actinomycetemcomitans has been reported by Kurita-Ochiai and Ochiai (Infect Immun 64: 50-54, 1996). To evaluate this factor, we cloned and characterized the gene encoding it. The immunosuppressive factor was screened from a genomic library of A. actinomycetemcomitans using an oligonucleotide probe based on the amino acid sequence of the factor. The clone obtained, pHI13, contained a 1.5 kbp fragment. The immunosuppressive factor located in its center. Southern blot analysis showed that this factor is common among A. actinomycetemcomitans strains. The open reading frame consisted of 324 bp coding for 107 amino acid residues. The relative molecular mass of the deduced amino acid sequence was calculated to be 11,595. BLAST analysis indicated that the amino acid sequence is highly homologous with those of thioredoxins from Haemophilus influenzae (76.6%), Neisseria meningitidis (67.3%), and Pseudomonas aeruginosa (59.3%). These results suggest that the 14 kDa immunosuppressive factor characterized in this study is a thioredoxin.

Potential mechanisms of susceptibility to periodontitis in tobacco smokers

Tobacco smoking is probably the most important, controllable environmental risk factor in periodontitis. It results in changes in the vascular, inflammatory, immune and healing responses. The degree of exposure to tobacco smoking can be measured in pack years or by measuring serum cotinine and nicotine levels. In a previous paper we reported elevated levels of serum soluble intercellular adhesion molecule-1 (sICAM-1) in smokers, regardless of periodontal status. Elevated sICAM-1 has been found to be a risk marker for cardiovascular disease. In the present paper we report the short-term effects of an episode of smoking on blood flow and levels of sICAM-1. Human volunteers included non-smokers, light smokers and heavy smokers. Relative blood flow was monitored in the gingivae and forehead skin using a laser Doppler flowmeter and serum levels of sICAM-1, cotinine and nicotine measured before during and up to 60 min following an episode of smoking. We could not provide evidence to support the theory that there is localized vasoconstriction within the gingival tissues. In contrast, there was a significant increase in blood flow in the forehead skin of light smokers which was not observed in non-smoking controls or in heavy smokers, suggesting a long-term tolerance in this latter group. The level of sICAM-1 remained unchanged during this episode, further suggesting a long-term effect. In a parallel group of subjects, we were able to demonstrate a direct significant correlation between sICAM and serum cotinine levels. These observations may be relevant to aetiological mechanisms in periodontitis and other smoking-associated diseases.