Generation of lys-gingipain protease activity in Porphyromonas gingivalis W50 is independent of Arg-gingipain protease activities.
(25/894)
Porphyromonas gingivalis, a black-pigmenting anaerobe implicated in the aetiology of periodontal disease, contains two loci, rgpA and rgpB, encoding the extracellular Arg-X specific proteases (RGPs, Arg-gingipains), and kgp, which encodes a Lys-X specific protease (KGP, Lys-gingipain). The rgpA and kgp genes encode polyproteins comprising pro-peptide and catalytic domain with large N- and C-terminal extensions which require proteolytic processing at several Arg and Lys residues to generate mature enzymes. The product of rgpB contains only a pro-peptide and the catalytic domain which requires processing at an Arg residue to generate active enzyme. An rgpA rgpB double mutant (E8) of P. gingivalis was constructed to study the role of RGPs in the processing of KGP. A kgp mutant (K1A) was also studied to investigate the role of KGP in the generation of RGPs. E8 was stable in the absence of the antibiotics tetracycline and clindamycin (selection markers for rgpA and rgpB, respectively) and exhibited the same pigmentation, colony morphology and identical growth rates to the parent W50 strain in the absence of antibiotics, in both complex and chemically defined media. The KGP activity of E8, grown in the absence of tetracycline, in whole cultures and in culture supernatants (up to 6 d) was identical to levels in W50. However, in the presence of tetracycline in the growth medium, the level of KGP was reduced to 50% of levels present in whole cultures of W50. Since tetracycline had no effect on RGP or KGP activity when incorporated into assay buffer, this effect is most likely to be on the synthesis of Kgp polypeptide. K1A was also stable in the absence of antibiotics but was unable to pigment, and remained straw-coloured throughout growth. RGP activity in whole cultures of K1A was identical to levels in W50, but RGP activity in 6 d culture supernatants was reduced to 50% of levels present in W50. Thus, although KGP is not required for generation of RGP activity from RgpA and RgpB polypeptides, its absence affects the release/transport of RGP into culture supernatant. (+info)
Human epithelial cell death caused by Actinobacillus actinomycetemcomitans infection.
(26/894)
The gingival sulcus is the shallow crevice around the tooth, and its epithelium is a gateway for initial bacterial infection in periodontal disease. Recent studies have shown that Actinobacillus actinomycetemcomitans invades an epithelial cell line, KB cells, in vitro. The aim of the present study was to clarify the changes in KB cells after A. actinomycetemcomitans infection. The cytotoxic effects of A. actinomycetemcomitans on KB cells were determined at 72, 96 and 120 h after infection by an MTT assay. Nuclear morphological changes were observed by staining with Hoechst 33258. Cytoplasmic histone-associated DNA fragmentation in the infected KB cells was determined by ELISA. A. actinomycetemcomitans was cytotoxic on KB cells, and condensation and degradation of the nuclei were observed. DNA fragmentation was increased after the infection. In addition, A. actinomycetemcomitans showed similar cytotoxic effects on human gingival epithelial cells. The present study demonstrated that A. actinomycetemcomitans induces apoptotic cell death of oral epithelial cells in an in-vitro culture system. This induced apoptosis might be involved in the initiation and progression of periodontitis. (+info)
A new murine model for atherosclerosis with inflammation in the periodontal tissue induced by immunization with heat shock protein 60.
(27/894)
It has recently become apparent that the anti-heat shock protein (HSP) antibody plays an important role in the pathogenesis of atherosclerosis. We studied whether immunization with human HSP60 could lead to atherosclerosis in mice. We attempted to induce atherosclerosis in C57BL/6NJcl mice by immunization with human HSP60 under a high-cholesterol diet. The size of fatty streak lesions was significantly enhanced in mice immunized with human HSP60 under a high-cholesterol diet relative to the number in control mice receiving a high-cholesterol diet alone. In addition, these new atherosclerotic model mice showed lesions of inflammation in the periodontal tissue. This new model may thus provide theoretical support for the clinical observation that patients suffering from periodontitis are frequently found to have atherosclerosis. The cytokine ratio of interferon-gamma/interleukin-4 in the high-cholesterol diet group was significantly higher than that in the standard chow group (p<0.05). This suggests the presence of a predominantly Th1-type immune response in atherosclerosis. (+info)
Smoking and periodontal disease.
(28/894)
Numerous investigations of the relationship between smoking and periodontal disease have been performed over the last 15 years, and there now exists a substantial body of literature upon which this current review is based. From both cross-sectional and longitudinal studies, there appears to be strong epidemiological evidence that smoking confers a considerably increased risk of periodontal disease. This evidence is further supported by the data emanating from patients who stop smoking. These patients have levels of risk similar to those of non-smokers. Numerous studies of the potential mechanisms whereby smoking tobacco may predispose to periodontal disease have been conducted, and it appears that smoking may affect the vasculature, the humoral immune system, and the cellular immune and inflammatory systems, and have effects throughout the cytokine and adhesion molecule network. The aim of this review is to consider the evidence for the association between smoking and periodontal diseases and to highlight the biological mechanisms whereby smoking may affect the periodontium. (+info)
Action on smoking--opportunities for the dental team.
(29/894)
In 1998, the UK government published a White Paper outlining a comprehensive range of measures to reduce smoking rates across the population. In the same year a detailed overview of the evidence base for smoking cessation activities within the NHS was published. Both these documents provide useful information for health professionals interested in developing their roles in smoking cessation and prevention. An increased risk for the development of oral malignancies and a susceptibility for the breakdown of periodontal tissues are the most significant effects of smoking on the mouth. This paper aims to highlight how dentists and their team members can become actively involved in efforts to reduce smoking. Opportunities at both a clinical and public health level are considered. (+info)
Disease activity and need for dental care in a capitation plan based on risk assessment.
(30/894)
This article describes a capitation model of care which would stimulate both dentists and patients to apply existing preventive knowledge. (+info)
Periodontal diseases among Quebec adults aged 35 to 44 years.
(31/894)
BACKGROUND: Very little information is available on periodontal diseases in Canadian adults. The purpose of this study was to estimate the prevalence of periodontal problems in Quebec adults aged 35 to 44. METHODS: A total of 2,110 randomly selected Quebec adults were examined between September 1994 and July 1995. The participation rate was 77% for the questionnaire and 44.5% for the oral examination. Measurements for gingival bleeding, calculus, epithelial attachment and periodontal pocket depths were taken for each tooth. RESULTS: More than 80% of examined persons presented with gingival bleeding on at least one tooth, and 75% presented with calculus on at least one tooth. The CPITN indicated that only 5.2% of individuals had no treatment needs, and that one out of 5 necessitated complex treatment. People with low family income, men and persons living in metropolitan areas are at higher risk of having at least one tooth with a pocket >6 mm. Dental health behaviours (regular dental visits, brushing and flossing frequency) were not significantly associated with the presence of periodontal pockets. Finally, individuals were relatively unaware of their periodontal problems. CONCLUSION: Increasing the population s awareness of periodontal diseases will be a major task for public health workers. The dental profession and the dental industry need to develop awareness campaigns to improve prevention, management and control of periodontal problems. It is especially important to target people at risk, in particular men and low-income groups. As well, dental schools and continuing education courses should focus on this problem with the aim of modifying dental practices. (+info)
Salivary histatin 5 is an inhibitor of both host and bacterial enzymes implicated in periodontal disease.
(32/894)
One of the salient features of periodontitis and gingivitis is the increase in the levels of bacterial and host-derived proteolytic enzymes in oral inflammatory exudates. This study evaluated the potential of histatin 5, a 24-residue histidine-rich salivary antimicrobial protein, to inhibit these enzymes. Using biotinylated gelatin as a substrate, histatin 5 was found to inhibit the activity of the host matrix metalloproteinases MMP-2 and MMP-9 with 50% inhibitory concentrations (IC50s) of 0.57 and 0.25 microM, respectively. To localize the domain responsible for this inhibition, three peptides containing different regions of histatin 5 were synthesized and tested as inhibitors of MMP-9. Peptides comprising residues 1 to 14 and residues 4 to 15 of histatin 5 showed much lower inhibitory activities (IC50, 21.4 and 20.5 microM, respectively), while a peptide comprising residues 9 to 22 showed identical activity to histatin 5 against MMP-9. These results point to a functional domain localized in the C-terminal part of histatin 5. To evaluate the effect of histatin 5 on bacterial proteases, a detailed characterization of histatin 5 inhibition of gingipains from Porphyromonas gingivalis was carried out using purified Arg- and Lys-specific enzymes. Kinetic analysis of the inhibition of the Arg-gingipain revealed that histatin 5 is a competitive inhibitor, affecting only the Km with a K(i) of 15 microM. In contrast, inhibition of Lys-gingipain affected both the Km and Vmax, suggesting that both competitive and noncompetitive competitive processes underlie this inhibition. The inhibitory activity of histatin 5 against host and bacterial proteases at physiological concentrations points to a new potential biological function of histatin in the oral cavity. (+info)