The host response to the microbial challenge in periodontitis: assembling the players

Effect of treatment of chronic periodontitis on levels of serum markers of acute-phase inflammatory and vascular responses

AIMS

Recent epidemiological work suggests an association between periodontal disease severity and cardiovascular disease risk. This study aimed to ascertain if circulating levels of cardiovascular and systemic inflammatory markers could be modified following treatment of periodontal disease.

METHOD

Adult subjects were recruited from those awaiting periodontal treatment and randomised to either immediate (test, n=24) or delayed treatment (control, n=15). Demographic and clinical data were collected and venous blood was taken before and either 6 weeks after completion of treatment or after an equivalent 3-month control period. Periodontal examination included probing depth, loss of attachment, plaque scores and bleeding scores. Blood was analysed to determine serum and plasma fibrinogen, C-reactive protein, sialic acid, tumour necrosis factor-alpha and interleukin -6 and -1beta. Effects of treatment were assessed by paired tests and analysis of variance by treatment group with baseline covariates.

RESULTS

Treatment improved plaque and bleeding scores and reduced probing depths (p<0.002). However, there were no statistically significant changes in levels of any of the systemic markers.

CONCLUSION

Improvement in periodontal health did not influence the levels of vascular markers.

Monocyte-derived RANTES is intrinsically elevated in periodontal disease while MCP-1 levels are related to inflammation and are inversely correlated with IL-12 levels

Bacteria colonizing tooth surfaces are essential in the induction of an inflammatory response in the periodontal tissues, but do not cause periodontitis in everyone, implicating differences in the host immune response. These possible differences were studied using lipopolysaccharide (LPS)-stimulated whole blood cell cultures (WBCC), which revealed a down regulation of monocyte derived interleukin-12 (IL-12p70) in untreated periodontitis patients and an up regulation after therapy. IL-12p70 is a crucial factor in the differentiation of Th1 cell responses. Since CC chemokines are able to influence the T cell differentiation via cytokine secretion in antigen-presenting cells, the production of CC chemokines in periodontitis was evaluated. Therefore WBCC were stimulated with LPS from Escherichia coli for 18 h and the levels of IL-12p70 and CC chemokines were measured in the supernatants by ELISA. Untreated periodontitis patients released 2 fold more RANTES (regulated on activation normal T cell expressed and secreted) (P = 0.01) and lower levels of IL-12p70 in comparison to controls (P < 0.05). A trend towards higher levels of macrophage chemoattractant protein-1 (MCP-1) (P = 0.07) was also seen in untreated periodontitis patients; while similar levels of monocyte derived chemokine (MDC) and macrophage inflammatory proteins-1 alpha and -1 beta (MIP-1 alpha and -1 beta) were found. After periodontal therapy no changes were seen with regard to MDC, MIP-1 alpha, MIP-1 beta and RANTES, whereas the MCP-1 levels decreased (P < 0.05) and the IL-12p70 levels strongly increased (P < 0.01). The data showed a consistent inverse correlation between the levels of MCP-1 and IL-12p70, and their proportional changes after therapy correlated with the clinical inflammatory response after therapy. This indicates that the disease state regulates the release of IL-12p70 and MCP-1 in E. coli LPS-stimulated WBCC. In contrast, the persistent augmented levels of RANTES after therapy are suggestive for an intrinsic behaviour.

IL-1 gene polymorphism and smoking as risk factors for peri-implant bone loss in a well-maintained population

The aim of the present study was (i) to investigate the relation between specific interleukin-1 (IL-1) gene polymorphisms and peri-implant bone loss at osseointegrated ITI(R) dental implants and (ii) to explore the association between these allelic variants of the IL-1 gene complex and peri-implant mucosal inflammation, in both smoking and non-smoking individuals. A sample of 90 consecutive Caucasian patients (aged 33-88 years), treated with at least one ITI-implant participated in this retrospective investigation. Standardized periapical radiographs were taken after prosthetic rehabilitation (133.6 days, SD 136.9 days) and at the time of the re-examination, on average 5.6 years (SD 2.5 years) thereafter. The radiographs were analyzed by a calibrated examiner for changes in peri-implant bone levels. The examiner was blind with respect to clinical parameters and IL-1 status. The distance between the implant shoulder and the first visible bone-implant contact (DIB) at the respective time points were measured using a computerized method. The absolute bone level difference during the years of service (ABL) and the annual bone loss (DeltaBL/year) were calculated for all the implants. Percentages of full mouth bleeding on probing (BOP), as well as of BOP calculated separately for teeth and implants, were determined for all visits and averaged for the entire observation period. Out of the total patient sample, there were 14 heavy smokers (= 20 cigarettes/day), 14 moderate smokers (5-19 cigarettes/day), 23 previous smokers (smoking cessation > 5 years) and 39 non-smokers. Twenty-eight (31.11%) patients were IL-1 genotype positive. Upon stratification for smoking status, significant differences were found for the variables ABL (P < 0.04, U-test) and DeltaBL/year (P < 0.04, U-test) between non-smokers and heavy smokers for the IL-1 genotype positive group but not for the IL-1 genotype negative group. Moreover, significant differences in ABL (P < 0.04, U-test) and DeltaBL/year (P < 0.04, U-test) were identified between former smokers and heavy smokers for the IL-1 genotype positive group. The differences in inflammatory parameters (BOP) did not reach statistical significance. This study suggests that in heavy cigarette smokers, carriage of a functionally significant IL-1 gene complex polymorphism is associated with an increased risk for peri-implant bone loss following prosthetic reconstruction and during the supportive periodontal care phase of the treatment.

Analysis of in situ proliferative activity in oral gingival epithelium in patients with xerostomia

BACKGROUND

Sjögren's syndrome is an autoimmune disease characterized by xerostomia and keratoconjunctivitis sicca. The relationship between xero-stomia and proliferative activity in human gingival epithelium is not known. Proliferating cell nuclear antigen (PCNA) is a nuclear protein associated with the cell cycle. Nuclear PCNA immunoreactivity is found in the proliferative compartment of normal tissues. The aims of this study were to evaluate PCNA expression in oral gingival epithelium of healthy and inflamed gingiva obtained from patients with Sjögren's syndrome, and to compare the results to age- and gender-matched subjects with normal salivary function.

METHODS

Eighteen Sjögren's syndrome patients and 28 controls (14 with chronic periodontitis and 14 with no clinical evidence of periodontal disease) were included in the study. Biopsies were obtained from both inflamed and healthy gingiva. The expression of PCNA was evaluated in formalin-fixed, paraffin-embedded gingival samples using an immunoperoxidase technique and PC10 monoclonal antibody to PCNA.

RESULTS

PCNA expression was observed both in the basal and suprabasal layers, and was found to be more prominent in the suprabasal layers. Proliferative index (PI) in inflamed gingiva was significantly lower in the Sjögren's syndrome group. However, no significant difference was observed between the study and control groups with respect to PI in healthy gingiva. In both groups, PI was found to be increased due to inflammation.

CONCLUSIONS

Our data indicate that proliferative activity is observed in the suprabasal layers and, less frequently, in the basal layer. Inflammation caused increased proliferative activity. However, this positive effect of inflammation on epithelial cell proliferation decreased significantly with a lack of saliva. Therefore, it appears that saliva-derived biological mediators may also contribute to increased proliferative activity observed during inflammation.

Neutrophil-mediated tissue injury in periodontal disease pathogenesis: findings from localized aggressive periodontitis

Neutrophils play a major role in the host response against invading periodontopathogenic microorganisms. Localized aggressive periodontitis (LAgP) is associated with various functional abnormalities of neutrophils. Based on the recent findings, LAgP neutrophils are not "hypofunctional" or "deficient." They are "hyperfunctional," and their amplified activity is responsible for the tissue destruction in periodontal disease. Several signal transduction abnormalities are associated with elevated neutrophil function in LAgP. There is a strong correlation between defective chemotaxis and decreased intracellular Ca2+ levels; total calcium-dependent protein Kinase C (PKC) activity of neutrophils is significantly lower than healthy subjects; and there is a marked increase in diacylglycerol (DAG) accompanied by a pronounced decrease in DAG kinase activity. In a separate set of experiments on the involvement of the inducible cyclooxygenase isoform (COX-2) and the role of novel lipid mediators in the pathogenesis of periodontal disease, crevicular fluid samples from LAgP patients were found to contain prostaglandin E2 (PGE2) and 5-LO-derived products, leukotriene B4 (LTB4), and the biosynthesis interaction product, lipoxin LXA4. Neutrophils from peripheral blood of LAgP patients, but not from healthy volunteers, also generated LXA4, suggesting that this immunomodulatory molecule may have a role in periodontal disease. Lipoxin generation and its relationship to PGE2 and LTB4 can be visualized as an important marker for the pathogenesis of periodontal disease. Thus, major advances in our understanding of the role of the neutrophil in host defense against periodontal organisms have been made through studies of LAgP. LAgP is used as an example of a severe periodontal disease that is related to abnormal neutrophil function. In this model, it appears that a hyperresponsiveness of the neutrophil, due to cell priming/predisposition, results in enhanced tissue damage.

Gingipains in the culture supernatant of Porphyromonas gingivalis cleave CD4 and CD8 on human T cells

Porphyromonas gingivalis has been shown to attack host defense systems through proteolytic cleavage of a wide variety of members of the systems. In this study, we examined the ability of P. gingivalis culture supernatant to alter the expression of human T cell surface proteins. As judged by flow cytometric analysis, detection of CD4 expression was completely eliminated by the supernatant, but CD8 was less sensitive. When the culture supernatant was added with reducing agents, proteolytic activity was enhanced, resulting in the cleavage of CD8. Mitogenic response of T cells to phytohemagglutinin or concanavalin A was decreased by the treatment of the cells with the culture supernatant of P. gingivalis. The three forms of gingipains (high molecular mass arginine-specific gingipain, arginine-specific gingipain 2 and lysine-specific gingipain) purified from the culture supernatant of P. gingivalis actively cleaved CD4 and CD8 on human T cells, indicating that proteolytic activity of the culture supernatant was due to gingipains. These results suggest that cysteine proteinases like gingipains released from P. gingivalis cleave T cell surface proteins and impede T cell function.

Induction of keratinocyte growth factor 1 Expression by lipopolysaccharide is regulated by CD-14 and toll-like receptors 2 and 4

Periodontal disease is a chronic inflammatory condition that is associated with increased concentrations of gram-negative pathogenic bacteria and epithelial cell proliferation. Regulation of this proliferation is poorly understood but is most likely controlled by locally expressed growth factors. Keratinocyte growth factor 1, an epithelium-specific growth factor, is expressed by gingival fibroblasts, and its expression is regulated in a concentration-dependent manner by lipopolysaccharide. In this study, induction of keratinocyte growth factor 1 protein expression was dependent on gingival fibroblast expression of membrane CD14 (mCD14) and Toll-like receptors 2 and 4. Lipopolysaccharides from Escherichia coli and Porphyromonas gingivalis induced membrane expression of CD14 at 1, 3, and 24 h. Specifically, lipopolysaccharide induced low mCD14 expression gingival fibroblasts to express mCD14 at a level consistent with that of high mCD14 expression cells. Functional studies with specific blocking antibodies for CD14 and Toll-like receptors 2 and 4 implicated all of these molecules in signal transduction. The rapid decrease in cell membrane expression of Toll-like receptors 2 and 4 after treatment with lipopolysaccharide was consistent with receptor internalization, and blocking of either of these receptors completely inhibited keratinocyte growth factor 1 protein expression. The transcription factors AP-1 and NF-kappaB were involved in lipopolysaccharide induction of keratinocyte growth factor 1 mRNA and protein expression. These results suggest that lipopolysaccharide may induce proliferation of periodontal epithelial cells by upregulating keratinocyte growth factor 1 expression via the CD14 and Toll-like receptor signaling pathway.

Coping with stress: its influence on periodontal disease

BACKGROUND

Various forms of stress behavior were documented and in patients with periodontitis their relationship with periodontal disease was investigated.

METHODS

Eighty-nine patients with different forms of chronic periodontitis were included in this retrospective case-control study. They were all undergoing periodontal treatment at the Department of Dental Prosthetics, University of Graz, or a private dental practice. The control group consisted of 63 persons employed in health care at the Clinic of Graz. All participants completed a stress coping questionnaire of 114 items and 19 actional and intrapsychic stress coping modes. The questionnaire served as a psychodiagnostic survey aimed at collecting data on stress coping strategies. Clinical attachment loss (CAL) served as the clinical parameter.

RESULTS

With the help of a factor analysis with a factorization and Varimax rotation, 5 factors were extracted from the 19 subtests. The reliability of the questionnaire was less than 0.70 only for subtests "escape" and "pharmaceutical drugs." Otherwise the internal consistency ranged between 0.74 and 0.92, and the retest reliability between 0.72 and 0.84. Subsequent assessment with the t test for independent random samples at the 5% level showed that patients differ significantly from controls in regard of factor 2 (active coping, P = 0.40) and 3 (distractive coping, P = 0.033), and that they differ very significantly from controls in regard of factor 4 (defensive coping, P = 0.000) and 5 (coping through aggression and pharmaceutical drugs, P = 0.007). In the statistical analysis of factors with regard to the severity of periodontal disease, the patients were divided into 2 groups (mild to moderate and severe). The t test for independent random samples showed significance for factor 4 (defensive coping) in that patients with a defensive coping style had greater attachment loss (pF4 = 0.04).

CONCLUSIONS

The data corroborate the thesis that periodontitis patients with inadequate stress behavior strategies (defensive coping) are at greater risk for severe periodontal disease. However, further investigations are required to confirm the significance of inappropriate coping styles with respect to the advancement of periodontal disease.

Sister chromatid exchange (SCE) analysis in periodontitis

BACKGROUND

Emerging data indicate that genetic factors may be associated with the etiopathogenesis of aggressive periodontitis. Sister chromatid exchange (SCE) is a sensitive method that might reflect an instability of DNA or a deficiency of DNA repair. The aim of the present study was to investigate SCE frequency of patients with different forms of periodontal disease and to determine whether this cytogenetic marker in patients with aggressive periodontitis can be differential compared to patients with chronic periodontitis and control subjects.

METHODS

SCE was analysed in peripheral blood lymphocyte chromosomes of 13 patients with generalised aggressive periodontitis (G-AP), 10 patients with chronic periodontitis (CP) and 10 control subjects. The periodontal parameters of probing depth, clinical attachment level, the presence of bleeding on probing and plaque were recorded. Peripheral blood lymphocytes obtained from both patient groups and control subjects were cultured in the presence of 5-Bromo-2-deoxyuridine in complete darkness for 72 h. For scoring SCE frequency, 20 metaphases were studied from each donor.

RESULTS

The frequency of SCE was found to be 6.7 +/- 0.9 per cell in patients with G-AP, 6.5 +/- 1.5 per cell in CP patients and 6.9 +/- 1.1 in control subjects. No statistically significant differences were found between groups (p > 0.05).

CONCLUSIONS

The data indicate that there the cyotogenetic damage in the aggressive type of periodontal disease is not greater than in chronic periodontitis and control subjects. Although no aberrant cytogenetic damage was observed in different forms of periodontitis compared to control, this does not discount the importance of other genetic factors in the pathogenesis of periodontal disease.

Enhanced neutrophil emigration and Porphyromonas gingivalis reduction following PGG-glucan treatment of mice

Periodontal disease is the consequence of a mixed Gram-negative infection in the gingival sulcus and has been associated with deficits in the neutrophil response. A novel, and heretofore untested, alternative approach to therapy is the use of biological-response modulators that enhance the neutrophil response. Poly-beta1-6-glucotriosyl-beta1-3-glucopyranose glucan (PGG-glucan) is an immunomodulator, derived from yeast, which specifically enhances neutrophil priming, phagocytosis and bacterial killing while failing to induce inflammatory cytokine expression. The hypothesis tested was that PGG-glucan could enhance host resistance to a Gram-negative periodontal pathogen, Porphyromonas gingivalis. Chambers were implanted subcutaneously in the dorsolumbar region of C57BL/6J mice and allowed to heal for 14 days. PGG-glucan was administered subcutaneously to one-half of the animals and saline to the other half. In the first set of experiments the chambers were inoculated with P. gingivalis (A7436) at 4 x 10 (6), 4 x 10 (7), and 4 x 10 (8) colony-forming units (CFU). In the second set of experiments the chambers were inoculated with 5 x 10 (8) CFU of either P. gingivalis or Streptococcus sanguis, a Gram-positive oral microbe that is not periodontopathic. Chambers were sampled over the following 2 weeks. The results demonstrated that: (1). bacterial CFU and neutrophils increased with increasing bacterial inoculum (P<0.02); (2). bacterial CFU were lower in the PGG-glucan-treated animals than in the saline controls (P<0.02); and (3). neutrophil counts were higher in the PGG-glucan-treated animals than in the saline controls (P<0.01). These results indicate that PGG-glucan significantly enhances neutrophil emigration and bacterial killing, thus decreasing the bacterial infection in this model system.

Localization of the chemokine interleukin-8 and interleukin-8 receptors in human gingiva and cultured gingival keratinocytes

Interleukin-8 (IL-8) has been implicated in a wide variety of diseases. Previous studies have demonstrated the expression of IL-8 in periodontal tissues, yet little is known about the exact source(s), mechanisms and factors involved in gingival expression of IL-8. Additionally, nothing is known about the presence and distribution of IL-8 receptors (IL-8R) in gingival cells. Therefore it was hypothesized that, in vivo, periodontal pathogens induce IL-8 expression from gingival keratinocytes (GK) which enhances leukocyte, microvascular endothelial cell (MVEC) and GK migration via specific IL-8 receptors present on these cells. The objective of the present study was to determine the distribution of IL-8 and IL-8R in gingival tissues and cultured human GK in vitro. Standard immunohistochemical and immunocytochemical techniques were utilized in order to localize IL-8 and its receptors CXCR-1 and CXCR-2 in archival gingival specimens (eight periodontitis and four non-inflamed controls) and in cultured gingival keratinocytes. It was demonstrated that, in vivo, IL-8 and IL-8R were present in gingival epithelium, MVEC and leukocytes. In vitro studies verified the above results, by showing expression of IL-8 and IL-8R in cultured gingival keratinocytes. It is concluded that IL-8 and IL-8 receptors are expressed in gingival epithelium both in vivo and in vitro. This new evidence indicates that epithelium plays a critical role in the host defense against invading pathogens and that keratinocytes can actively respond to IL-8 and other host cytokines, via specific receptors.

Multiserotype enzyme-linked immunosorbent assay as a diagnostic aid for periodontitis in large-scale studies

Periodontitis is a common chronic oral infection caused by gram-negative bacteria, including Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. Periodontitis evokes inflammatory host response locally in the periodontium but also systemically. The systemic humoral antibody response against oral pathogens can conveniently be measured by an immunoassay. The aim of the study was to measure serum immunoglobulin G class antibodies against A. actinomycetemcomitans and P. gingivalis by an enzyme-linked immunosorbent assay (ELISA) in which mixtures of several serotypes of the pathogens were used as antigens to avoid biasing of the results in favor of a particular strain. For A. actinomycetemcomitans the antigen consisted of six strains representing serotypes a, b, c, d, and e and one nonserotypeable strain. In the P. gingivalis ELISA, antigens representing serotypes a, b, and c were used. Serum samples from 90 subjects, including 35 samples from patients with diagnosed periodontitis, 10 samples from periodontally healthy controls, and 45 samples from randomly selected apparently healthy volunteers (referred to as "healthy subjects"), were tested. For both pathogens the antibody levels (means +/- standard deviations) of the patients--xpressed as area under the dilution curve--were significantly higher than those for healthy controls or healthy subjects, with values for A. actinomycetemcomitans and P. gingivalis, respectively, as follows: patients, 22.60 +/- 9.94 mm(2) and 26.72 +/- 11.13 mm(2); healthy controls, 9.99 +/- 3.92 mm(2) and 6.90 +/- 3.38 mm(2); and healthy subjects, 16.85 +/- 6.67 mm(2) and 8.51 +/- 4.23 mm(2). The serotype mixture ELISA is suitable for measuring antibodies against periodontal pathogens in large epidemiological studies in order to evaluate the role of periodontitis as a risk factor for other diseases.

Infection-mediated early-onset periodontal disease in P/E-selectin-deficient mice

BACKGROUND

Retrospective and correlation studies suggest that early-onset periodontal disease may be due to a deficiency in phagocyte function, a pathogenic oral biofilm, and/or dysregulated gingival cytokine expression. Increased susceptibility to periodontal disease is therefore thought to result from multiple risk factors.

METHODS

We tested this hypothesis prospectively using P/E-selectin adhesion molecule deficient mice that mimic the human syndrome leukocyte adhesion deficiency II.

RESULTS

Our studies demonstrate that, in comparison to wild type animals, P/E-/- mice exhibit: spontaneous, early onset alveolar bone loss which is significant by 6 weeks of age; a 10-fold elevation in bacterial colonization of their oral cavities; and elevated gingival tissue levels of the bone resorptive cytokine IL-1alpha. Alveolar bone loss is completely prevented by prophylactic antibiotic therapy.

CONCLUSIONS

These experiments provide the first prospective evidence for the multiple risk factor hypothesis of periodontal disease, and validate the first animal model for early onset periodontitis in which both the microbiota and host response can be systematically manipulated. P/E-/- animals should be useful in testing the virulence of putative periodontal pathogens, in determining the role of host resistance factors in periodontitis, in exploring the proposed relationship(s) between infection mediated alveolar bone loss and systemic health disorders, and exploring their genetic relationships.

Inhibition of proteolytic, serpinolytic, and progelatinase-b activation activities of periodontopathogens by doxycycline and the non-antimicrobial chemically modified tetracycline derivatives

BACKGROUND

Tetracyclines, particularly doxycycline (Doxy), and their non-antimicrobial chemically-modified derivatives (CMTs) inhibit the activities of human matrix metalloproteinases (MMPs), and reduce the severity and progression of periodontal disease in animal models and humans. In this study, the effects of Doxy and CMT-1, -3, and -5 on proteolytic, serpinolytic, and progelatinase-B activation activities of potent periodontopathogens were studied.

METHODS

The effect of Doxy and CMTs (0.5 to 50 microM) on proteolytic activities were investigated by incubating bacteria with chromogenic substrates or human serum albumin. A collagenolytic fraction of Porphyromonas gingivalis was used to evaluate the effect of these substances on collagenolytic (type I collagen) and serpinolytic (alpha1-proteinase inhibitor) activities. Lastly, the effect of Doxy on progelatinase-B (pro-MMP-9) activation by purified proteinases from P. gingivalis and Treponema denticola was investigated by SDS-PAGE/Western immunoblotting.

RESULTS

Doxy and CMTs, except CMT-5 which lacks the structural elements required for cation chelation, inhibited Arg- and Lys-gingipain activities as well as collagenolytic activity of P. gingivalis. Doxy and CMTs did not markedly affect the chymotrypsin-like activity of T. denticola but inhibited its trypsin-like activity. In addition, degradation of human serum albumin by cells of P. gingivalis and T. denticola was strongly inhibited by Doxy and CMT-1. Doxy and CMT-1 also inhibited the inactivation of alpha1-proteinase inhibitor (serpinolytic activity) by a collagenolytic fraction of P. gingivalis. Lastly, Doxy prevented the latent to active conversion of human neutrophil progelatinase-B (pro-MMP-9) by Arg-gingipains A/B of P. gingivalis but not by the chymotrypsin-like proteinase of T. denticola.

CONCLUSIONS

Data from this study suggest that Doxy and CMTs have the potential to inhibit the periodontopathogenic bacterial proteinases, which contribute to tissue destruction cascades during periodontitis directly and indirectly by triggering the host response.

Effect of avocado and soybean unsaponifiables on gelatinase A (MMP-2), stromelysin 1 (MMP-3), and tissue inhibitors of matrix metalloproteinase (TIMP- 1 and TIMP-2) secretion by human fibroblasts in culture

BACKGROUND

In inflamed periodontal tissues, gingival fibroblasts are able to express matrix metalloproteinases (MMPs) and their natural inhibitors, tissue inhibitors of matrix metalloproteinases (TIMPs). They can also respond to growth factors and cytokines. In this study, the in vitro effects of avocado and soybean unsaponifiable residues (ASU), their fractions (avocado unsaponifiable [ASF] or soy unsaponifiable [SSF]) on MMP-2 and MMP-3, and the activity and secretion of their inhibitors TIMP-1 and TIMP-2 were investigated using cultured human gingival fibroblasts.

METHODS

Gingival fibroblasts were cultured for 72 hours with ASU, ASF, and SSF at concentrations of 0. 1, 0.5, 2.5, 5, and 10 microgram/ml of culture medium, after pretreatment or no pretreatment for 1 hour with interleukin-1beta (IL-1beta). MMP-2 and MMP-3 were detected and quantified in the culture media after zymography and image analysis. TIMP-1, TIMP-2, MMP-2, and MMP-3 were also evidenced by dot blotting and quantified by image analysis.

RESULTS

In the absence of IL-1beta, a slight decrease in the secretion of MMP-2 was observed with lower doses of ASU, ASF, and SSF. The decrease of MMP-3 secretion was clearly marked with all fractions especially at low concentrations (0.1 and 2.5 microgram/ml). A slight decrease in TIMP-2 secretion was seen for low doses of ASU, ASF, and SSF, while a small increase was seen at higher concentrations. Concerning TIMP-1, no significant variation was observed in culture medium for low concentrations, and a decrease was noted for 5 and 10 microgram/ml of ASU, ASF, and SSF. As anticipated, IL-1beta induced a marked release of MMP-2, MMP-3, and TIMP-1, but no variation for TIMP-2 was seen. ASU, ASF, and SSF reversed the IL-1beta effect on gingival fibroblasts for MMP-2 and MMP-3, particularly with doses varying from 0.1 to 2.5 microgram/ml and for TIMP-1, particularly with doses varying from 2.5 to 10 microgram/ml.

CONCLUSIONS

These findings suggest a potential role for avocado and soy unsaponifiable extracts to prevent the deleterious effects of IL-1beta that occur during periodontal diseases.

Treatment of periodontal disease and control of diabetes: an assessment of the evidence and need for future research

Evidence points to an increased cytokine response in type 2 diabetes, especially the proinflammatory cytokines interleukin (IL)-1 beta, IL-6, and tumor necrosis factor (TNF)-alpha. Genetics, age, and, nutrition are important signals for this increased response and as reported more recently, infections and inflammation. Persistent elevation of IL-1 beta, IL-6, and TNF-alpha in the diabetic state have an effect on the liver, stimulate the release of acute-phase proteins, produce the characteristic dysregulation of lipid metabolism associated with type 2 diabetes, and have effects on pancreatic beta cells as well. In addition, TNF-alpha, a potent inhibitor of the tyrosine kinase activity of the insulin receptor, has been implicated as an etiologic factor for insulin resistance. Collectively, the evidence supports a role for cytokine elevation in the pathophysiology and metabolic abnormalities associated with diabetes. Periodontitis is an infection that is twice as prevalent in diabetic individuals compared to non-diabetics. Porphyromonas gingivalis, one of the microorganisms responsible for this infection, is able to invade endothelial cells and is a potent signal for monocyte and macrophage activation. Thus, once established in the diabetic host, this chronic infection complicates diabetes control and increases the occurrence and severity of microvascular and macrovascular complications. Unlike treatment of acute infections, modalities of treatment for chronic infections are a matter of debate. Evidence indicates that mechanical removal of subgingival infection does not result in complete elimination of periodontal infection and consequently there is no effect on diabetes control measured as reduction in glycated hemoglobin. On the other hand, studies incorporating systemic antibiotics as adjuncts to mechanical debridement result in a reduction of P. gingivalis to nondetectable levels and a concomitant reduction in glycated hemoglobin, independent of the hypoglycemic effects of diabetes drugs or insulin. The evidence supports the notion that treatment of chronic periodontal infection is essential in the diabetic patient. Assessment of infection status in diabetic patients is fundamental for appropriate treatment decisions.

Yeasts in periodontal pockets

OBJECTIVES

The presence of yeasts in periodontal pockets has been described in a few studies. The association between yeasts and putative periodontal pathogens is not well described. This study aims at assessing the prevalence of yeasts in periodontal pockets and possible associations with the clinical conditions of the sampled sites and other micro-organisms present.

MATERIAL AND METHODS

2 subject groups form the basis for this study. The 1st comprises results from microbiological samples from periodontal pockets of 128 subjects. The 2nd originates from 126 periodontal patients with untreated pockets. Microbiological identification was performed after cultivation on blood and Sabouraud agar plates, and "checkerboard" DNA-DNA hybridisation.

RESULTS

The prevalence of subjects with yeasts in the pockets was 15.6% and 17.5% in the 2 groups respectively and was inconsistent according to gender. No correlation was found between age and the presence of yeasts. Eubacterium saburreum was weakly correlated with presence of yeasts (r=0.194 p=0.03). Yeasts were rarely found in both samples from the same individual.

CONCLUSIONS

Our results indicate that yeasts can be expected to be present in periodontal pockets in one out of 6 periodontal patients independent of gender and age. Eubacterium saburreum seems to occur frequently together with yeasts.

Cytokine gene expression in chronic periodontitis

BACKGROUND

Cytokines play an important rôle in controlling inflammatory processes and tissue homeostasis. Periodontitis, as any other chronic inflammatory disease, results from a disarrangement of host factors, mainly cytokines and the initiating agent. Modulation of the cytokines is not only controlled by the host but also by infecting bacteria and their products.

AIM

In the present study, we examined the cytokine mRNA expression profiles in six patients, each presenting sites affected with (1) severe progressive periodontitis, (2) chronic, but stable periodontal lesions, and (3) with healthy sites. Analysis using a quantitative RT-PCR included IFN-gamma, IL-1beta, IL-2, IL-4, IL-5, IL-6, and TNF-alpha.

MATERIAL AND METHODS

6 patients with chronic periodontitis were following treatment observed for a period of six years for local sites staying healthy, local sites with periodontal pathology but without signs of progression of attachment loss and sites with verified progression were biopsied. The biopsies were lyzed and analyzed for levels of cytokine mRNAs.

RESULTS

Results revealed considerable variation not only between patients, but also between individual sites. Each patient's site has thus to be looked at as an independent entity.

CONCLUSIONS

The local action of cytokines, which is heavily dependent on recruitment, interaction and activation of immunocompetent cells can explain the site-specific nature of cytokine expression. Cytokine data from individual sites together with the local clinical status and data from the literature demonstrate the complexity of periodontal disease pathogenesis. To gain insight to specific mechanisms further studies are needed.

Chemokines in human periodontal disease tissues

An immunoperoxidase technique was used to examine IP-10 (interferon-gamma inducible protein 10), RANTES (regulated on activation normal T cell expressed and secreted), MCP-1 (monocyte chemoattractant protein-1), and MIP-1 alpha (macrophage inflammatory protein-1 alpha) in gingival biopsies from 21 healthy/gingivitis and 26 periodontitis subjects. The samples were placed into 3 groups according to the size of infiltrate. MIP-1 alpha+ cells were more abundant than the other chemokines with few MCP-1+ cells. The mean percent MIP-1 alpha+ cells was higher than the percent MCP-1+ cells (P = 0.02) in group 2 (intermediate size infiltrates) lesions from periodontitis subjects, other differences not being significant due to the large variations between tissue samples. Analysis of positive cells in relation to CD4/CD8 ratios showed that with an increased proportion of CD8+ cells, the mean percent MIP-1 alpha+ cells was significantly higher in comparison with the mean percent RANTES+ and MCP-1+ cells (P < 0.015). Endothelial cells were MCP-1+ although positive capillaries were found on the periphery of infiltrates only. Keratinocyte expression of chemokines was weak and while the numbers of healthy/gingivitis and periodontitis tissue sections positive for IP-10, RANTES and MCP-1 reduced with increasing inflammation, those positive for MIP-1 alpha remained constant for all groups. In conclusion, fewer leucocytes expressed MCP-1 in gingival tissue sections, however, the percent MIP-1 alpha+ cells was increased particularly in tissues with increased proportions of CD8 cells and B cells with increasing inflammation and also in tissues with higher numbers of macrophages with little inflammation. Further studies are required to determine the significance of MIP-1 alpha in periodontal disease.

Fluid dynamics of gingival tissues in transition from physiological condition to inflammation

BACKGROUND

An increase in gingival sulcular fluid filtration is a common clinical sign of early gingivitis. The aim of this study was to describe the fluid dynamics of the gingival interstitial tissues at the level of the sulcus in the transition towards inflammation.

METHODS

In 13 anesthetized rabbits, a silk ligature was placed around incisors close to the gingival margin, in order to prevent mechanical cleaning of plaque deposition. After 2 to 7 days, animals were anesthetized and interstitial fluid pressure measured using glass micropipettes connected to a servonull pressure system at the level of the free and attached gingiva.

RESULTS

Interstitial pressure was 3.8 +/- 2.9 cmH2O, significantly higher than the normal physiological value (about -1 cmH2O). Colloid osmotic pressure of interstitial fluid samples collected using the wick technique was measured using an osmometer whose membrane had a molecular cut-off of 30 kD and averaged 12.8 +/- 2.8 cmH2O (unchanged relative to control). Mean gingival sulcular fluid flow, measured by placing a PE tube (0.5 mm OD, 0.28 mm ID) in the sulcus, was 0.16 +/- 0.12 microl/h; the mean colloid osmotic pressure was 13.6 +/- 6.6 cmH2O, corresponding to a protein concentration of approximately 2.8 g/dl. Proteins of gingival fluid may leak from inflamed gingival interstitium or derive from bacteria of dental plaque. Histological analysis of gingival biopsies showed neutrophilic polymorphonuclear leukocyte infiltrates in both the dermis and epidermis layer.

CONCLUSIONS

Based on hydraulic and colloid osmotic data, the Starling pressure gradient favored filtration from gingival interstitium to the sulcular space, a condition opposite to that observed in healthy gingiva where fluid filtration is absent.

Toll-like receptor 4-deficient mice have reduced bone destruction following mixed anaerobic infection

C3H/HeJ mice have an impaired ability to respond to lipopolysaccharide (LPS) due to a mutation in the gene that encodes Toll-like receptor 4 (TLR4). The effect of TLR4 deficiency on host responses to endodontic infections is unknown. In the present study, we compared periapical bone destruction, sepsis, and inflammatory cytokine production in LPS-hyporesponsive C3H/HeJ and wild-type control C3H/HeOuJ mice. The mandibular first molars of both strains were subjected to pulpal exposure and infection with a mixture of four anaerobic pathogens, Prevotella intermedia, Fusobacterium nucleatum, Streptococcus intermedius, and Peptostreptococcus micros. At sacrifice on day 21, TLR4-deficient C3H/HeJ mice had significantly reduced periapical bone destruction compared to wild-type C3H/HeOuJ mice (P < 0.001). The decreased bone destruction in C3H/HeJ correlated with reduced expression of the bone resorptive cytokines interleukin 1alpha (IL-1alpha) (P < 0.01) and IL-1beta (P < 0.05) as well as the proinflammatory cytokine IL-12 (P < 0.05). No significant differences were seen in the levels of gamma interferon, tumor necrosis factor alpha (TNF-alpha), or IL-10 between the two strains. The expression of IL-1alpha, IL-1beta, TNF-alpha, IL-10, and IL-12 were all significantly reduced in vitro in macrophages from both TLR4-deficient C3H/HeJ and C57BL/10ScNCr strains, compared to wild-type controls. Notably, the responses of TLR4-deficient macrophages to both gram-positive and gram-negative bacteria were similarly reduced. Neither C3H/HeJ nor C3H/HeOuJ mice exhibited orofacial abscess development or infection dissemination as determined by splenomegaly or cachexia. We conclude that intact TLR function mediates increased proinflammatory responses and bone destruction in response to mixed anaerobic infections.

The oral cavity as a reservoir of bacterial pathogens for focal infections

Dental procedures, but more importantly, oral infections and poor oral health can provoke the introduction of oral microorganisms into the bloodstream or the lymphatic system. The subsequent attachment and multiplication of these bacteria on tissues or organs can lead to focal oral infections. Pathogenic agents may also remain at their primary oral site but the toxins liberated can reach an organ or tissue via the bloodstream and cause metastatic injury. Finally, metastatic inflammation may result from an immunological injury caused by oral bacteria or their soluble products that enter the bloodstream and react with circulating specific antibodies to form macromolecular complexes.

Chemokine expression in Porphyromonas gingivalis-specific T-cell lines

Autologous non-T cells (monocytes and B cells) were added to Porphyromonas gingivalis-specific T cell lines established from 9 healthy adults together with P. gingivalis outer membrane antigens for 4-6, 16-18, 24 and 48 h. Flow cytometry was employed to analyze the CD4 and CD8 cells, monocytes and B cells for intracytoplasmic IP-10 (interferon-gamma inducible protein 10), MCP-1 (monocyte chemoattractant protein 1), MIP-1 alpha (macrophage inflammatory protein 1 alpha) and RANTES (regulated on activation normal T cell expressed and secreted) at the four time periods. All cell types were positive for each chemokine throughout the 48-h time period. There were significantly fewer MCP-1-positive cells compared with the other 3 chemokines. However, the percentages of MCP-1, MIP-1 alpha- and RANTES-positive CD8 cells were significantly higher than the percentages of positive CD4 cells in all cultures. IP-10-positive CD4, CD14-positive monocytes and CD19-positive B cells were predominant compared with MIP-1 alpha- and RANTES-positive cells at 24 h. In conclusion, the present study has shown that P. gingivalis-specific T cells, monocytes and B cells produce chemokines in response to P. gingivalis outer membrane antigens, IP-10 being predominant, with MCP-1 being significantly reduced in comparison with IP-10, MIP-1 alpha and RANTES. Increased percentages of CD8 cells were induced to produce chemokines in comparison with CD4 cells, indicating a more preferential action on CD8 rather than CD4 cells.

Human herpesviruses and Porphyromonas gingivalis are associated with juvenile periodontitis

BACKGROUND

Although herpesviruses have been associated with adult periodontitis, their relationship with juvenile periodontitis (JP) has not been established. This case-control study examined possible associations between JP and pathogenic bacteria, the human cytomegalovirus (HCMV), and the Epstein-Barr type 1 virus (EBV-1).

METHODS

Subjects were participants in a larger survey of schoolchildren in North-Central Jamaica. Subgingival plaque samples from 15 subjects with JP, 20 with incipient periodontitis (IP), and 65 randomly-selected healthy controls were assayed for Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans using a 16S rRNA polymerase chain reaction (PCR) identification method, and for HCMV and EBV-1 using nested PCR identification.

RESULTS

Strong bivariate associations were found between JP and P. gingivalis (odds ratio [OR] = 12.7; 95% CI = 2.6, 61.4), HCMV (OR = 10.0; 95% CI = 2.7, 36.3), and A. actinomycetemcomitans (OR = 8.0; 95% CI = 2.3, 27.5), but not EBV-1. In multivariate analyses, P. gingivalis remained a significant explanatory variable (OR = 7.8; 95% CI = 1.5, 40.9); however, the associations were marginal for HCMV (OR = 4.6; 95% CI = 0.9, 22.7), and non-significant for A. actinomycetemcomitans (OR = 2.0; 95% CI = 0.4, 9.7). The associations with JP and the extent of attachment loss were even stronger when both P. gingivalis and HCMV were detected together. P. gingivalis (OR = 3.9; 95% CI = 1.3, 12.0) and EBV-1 (OR = 3.3; 95% CI = 1.0, 10.3) were the only significant explanatory variables in the multivariate analysis of IP.

CONCLUSIONS

P. gingivalis is the strongest and most stable indicator of periodontitis in Jamaican adolescents. Co-infection with P. gingivalis and HCMV appears to be particularly deleterious to periodontal health.

Porphyromonas gingivalis induction of mediator and cytokine secretion by human gingival fibroblasts

We hypothesized that bacterial viability and strain characteristics of Porphyromonas gingivalis could affect the induction of pro-inflammatory mediator secretion by human gingival fibroblast cultures. Both killed and viable P. gingivalis elicited production of prostaglandin E2, interleukin-1 beta (IL-1 beta), IL-6 and IL-8, although killed P. gingivalis induced generally higher levels, particularly IL-6 and IL-8, compared with the viable bacteria. P. gingivalis strains, which exhibited wild-type levels of trypsin-like protease activity, stimulated human gingival fibroblasts to secrete increased levels of prostaglandin E2 and IL-1 beta, although minimal levels of IL-6 and IL-8 were noted in supernatants from the gingival fibroblast cells. P. gingivalis strains BEI and NG4B19, which have either decreased or undetectable levels of trypsin-like protease, respectively, induced significantly greater IL-6 and IL-8 levels in gingival fibroblast cultures compared with the other strains. The ability of antibody to P. gingivalis to alter human gingival fibroblast production of pro-inflammatory mediators was tested using nonhuman primate antisera. Both immune and nonimmune sera altered the P. gingivalis-generated pattern of mediators from the gingival fibroblasts. We conclude that: (i) viable and killed P. gingivalis were capable of inducing various pro-inflammatory cytokines from human gingival fibroblasts; (ii) strain differences in cytokine induction were noted, and the expression of a trypsin-like protease activity was related to decreased extracellular levels of IL-6 and IL-8; and (iii) the presence of serum, particularly with specific antibody to P. gingivalis, significantly altered human gingival fibroblast cytokine production compared with P. gingivalis alone.

Changes in the periodontal status of patients undergoing bone marrow transplantation

BACKGROUND

Patients receiving an HLA-matched bone marrow transplant (BMT) from a relative or unrelated donor undergo a permanent alteration of their immune system, followed by a prolonged period of immunodeficiency. This study aimed to examine alterations in the periodontal status of patients over 6 months post-bone marrow transplantation.

METHODS

Thirty-seven patients scheduled for bone marrow transplantation participated in this study. One calibrated examiner carried out periodontal examinations (clinical and radiographic) immediately prior to and at 3 and 6 months after transplantation. All patients followed an intense oral care program. Subgingival plaque samples were analyzed by enzyme-linked immunosorbent assay (ELISA) for the presence of Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, and Prevotella intermedia. Data were subjected to statistical analyses to determine the relationships between the frequency distribution of the radiographic and clinical variables over time.

RESULTS

Gains in clinical attachment level (CAL) of > or =2 mm at 4 or more sites from baseline to 6 months post-BMT were noted in 9/16 patients (56%), while 6/16 (38%) patients experienced a loss of CAL > or =2 mm at 4 or more sites in the same period. At a site level, 4.8% of sites exhibited a gain in CAL > or =2 mm between baseline and 3 months post-BMT while 2.3% of sites showed a loss of CAL > or =2 mm in the same period. From baseline to 6 months, a gain in CAL of > or =2 mm was recorded at 3.1% of sites, and 2.4% of sites experienced a loss of > or =2 mm. A significant improvement in the gingival index occurred between all sequential time periods when assessed at a site level. At a patient level, 11/18 (61%) patients showed a significant change in gingival index between baseline and 3 months and 10/16 (63%) between baseline and 6 months. There was no significant relationship between clinical changes and the prevalence of the periodontal pathogens at the various time periods.

CONCLUSIONS

An improvement in periodontal health was recorded between baseline and 6 months post-transplantation. Most of the improvement in periodontal status was noted in the first 3 months after BMT, with a slight decline in periodontal health between 3 and 6 months post-transplant. No significant alteration was noted in the prevalence of periodontal pathogens during the study period.

Inhibition of the activities of matrix metalloproteinases 2, 8, and 9 by chlorhexidine

Matrix metalloproteinases (MMPs) are a host cell-derived proteolytic enzyme family which plays a major role in tissue-destructive inflammatory diseases such as periodontitis. The aim of the present study was to evaluate the inhibitory effect of chlorhexidine (CHX) on MMP-2 (gelatinase A), MMP-9 (gelatinase B), and MMP-8 (collagenase 2) activity. Heat-denatured type I collagen (gelatin) was incubated with pure human MMP-2 or -9 activated with p-aminophenylmercuric acetate (APMA), and the proteolytic degradation of gelatin was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Coomassie blue staining. The effect of CHX on MMP-8 activity was also studied with a cellular model addressing the ability of phorbol myristate acetate (PMA)-triggered human peripheral blood neutrophils (polymorphonuclear leukocytes [PMNs]) to degrade native type I collagen. CHX inhibited the activities of both gelatinases (A and B), but MMP-2 appeared to be more sensitive than MMP-9. Adding calcium chloride to the assay mixtures almost completely prevented the inhibition of MMP-9 activity by CHX, while the inhibition of MMP-2 activity could be reversed only when CHX was used at a low concentration. This observation suggests that CHX may act via a cation-chelating mechanism. CHX dose-dependently inhibited collagenolytic activity of MMP-8 released by PMA-triggered PMNs. MMP-8 without APMA activation was inhibited clearly more efficiently than APMA-activated MMP-8. Our study suggests that the direct inhibition of the MMPs' activities by CHX may represent a new valuable effect of this antimicrobial agent and explains, at least in part, the beneficial effects of CHX in the treatment of periodontitis.

Actinobacillus actinomycetemcomitans toxin induces both cell cycle arrest in the G2/M phase and apoptosis

We found that the culture supernatant of the periodontopathic bacterium Actinobacillus actinomycetemcomitans had a cytotoxic effect on several cell lines. In this study, we purified the toxin from the culture supernatant of A. actinomycetemcomitans Y4 by a four-step procedure: ammonium sulfate precipitation, POROS HQ/M column chromatography, polymyxin B matrix column chromatography, and Mono-Q column chromatography. The purified toxin gave two major bands of protein with molecular masses of 80 and 85 kDa upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The mechanism of cell death of the B-cell hybridoma cell line HS-72 was examined by observing changes in nuclear morphology, an increase in the proportion of fragmented DNA, and the typical ladder pattern of degraded chromosomal DNA, indicating the induction of apoptosis. Overexpression of human Bcl-2 suppressed apoptosis in HS-72 cells, indicating that the toxin from A. actinomycetemcomitans induces apoptosis by a Bcl-2-inhibitable mechanism. Flow cytometric analysis revealed that the toxin caused cell cycle arrest in the G2/M phase and apoptosis in HS-72 cells. In addition, aurintricarboxylic acid, a DNA endonuclease inhibitor, markedly decreased the percentage of apoptotic cells but had no effect on cell cycle arrest in the G2/M phase. Taken together, these findings suggest that the toxin from A. actinomycetemcomitans could mediate the development of periodontal diseases through cell cycle arrest in the G2/M phase and apoptosis in B lymphocytes of periodontal tissue.

Characterization of immunocompetent cells in the diseased canine periodontium

The beagle dog with naturally occurring periodontal disease is one of the most widely used animal models in periodontal research for histological studies on disease pathogenesis and on the effect of potential therapeutic regimens. However, previous studies were restricted to morphological assessment of immunocompetent cells because of the lack of available cell-specific markers. In this study we systematically characterized the specificity and immunoreactivity of a panel of anti-human antibodies for identification (ABC method) of immunocompetent cells in formalin-fixed, EDTA-decalcified, paraffin-embedded inflamed periodontal tissues obtained from six beagle dogs. Canine lymph nodes and a panel of different human tissues served as positive controls. Polyclonal anti-CD3 immunolabeled canine T-lymphocytes specifically. Anti-CD79alpha (clone HM57) reacted with B-lymphocytes and plasma cells, and CD79alpha (clone JCP117) showed no staining in canine tissues. Neutrophils, monocytes, small macrophages, and keratinocytes reacted with an anti-myeloid/histiocyte antibody (clone MAC387). Anti-CD68 (clones PG-M1 and EBM11) immunolabeled large macrophages and plasma cells. Clone EBM11 also stained osteoclasts and cementoclasts. With the exception of JCB117, all antibodies revealed similarly favorable immunolabeling of canine and human immunocompetent cells. Long-term EDTA decalcification appeared to weaken immunostaining of plasma cells with HM57. MAC387 and CD68 can be used to distinguish macrophages in different differentiation stages in canine periodontal tissues. (J Histochem Cytochem 46:1443-1454, 1998)

Gingival epithelial cells increase interleukin-8 secretion in response to Actinobacillus actinomycetemcomitans challenge

Periodontal diseases result from the interaction of bacterial pathogens with the host gingival tissues. The role of gingival epithelial cells in the initiation of host defense mechanisms after encountering oral bacteria has not been investigated. Actinobacillus actinomycetemcomitans is a key periodontal pathogen that adheres to and invades oral epithelial cells. Thus, we examined whether gingival epithelial cells increase secretion of the potent neutrophil chemoattractant interleukin-8 (IL-8) following A. actinomycetemcomitans challenge. Normal human oral keratinocytes (NHOK), isolated from gingival tissue, and 3 oral epithelial cell lines (HOK-18A, HOK-16B-BaP-T1, and HEp-2) were co-cultured with A. actinomycetemcomitans for 2 hours to allow bacteria-epithelial cell interactions. The epithelial cells were then washed, and fresh medium with gentamicin was added to kill extracellular bacteria. Cell cultures were further incubated for 24 hours before the supernatant was collected for IL-8 detection with ELISA. The results showed that IL-8 secretion increased 2- to 7-fold 24 hours after bacterial challenge. The highest IL-8 secretion was at the multiplicity of infection (MOI) of 1,000:1 in bacterial dose response studies using HOK-16B-BaP-T1 cells. Time-course studies revealed that IL-8 secretion rapidly reached a maximum level 6 hours after bacterial challenge and subsequently decreased to basal levels. These data indicate that gingival epithelial cells are capable of upregulating IL-8 expression rapidly in response to A. actinomycetemcomitans challenge and thus may facilitate the recruitment of neutrophils as a host defense mechanism.

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.