Arachidonic acid metabolism in inflamed gingiva and its inhibition by anti-inflammatory drugs

The role of the microbiota in periodontal disease

The last decade has witnessed unparalleled advances in our understanding of the complexity of the oral microbiome and the compositional changes that occur in subgingival biofilms in the transition from health to gingivitis and to destructive periodontal disease. The traditional view, which has held sway for the last 2 decades, that disease is characterized by the outgrowth of a consortium, or consortia, of a limited number of potentially pathogenic organisms, has given way to an alternative paradigm. In this new view, the microbiological changes associated with disease represent whole-scale alterations to the overall microbial population structure and to the functional properties of the entire community. Thus, and in common with other microbially mediated diseases of the gastrointestinal tract, the normally balanced, symbiotic, and generally benign commensal microbiome of the tooth-associated biofilm undergoes dysbiosis to a potentially deleterious microbiota. Coincident with progress in defining the microbiology of these diseases, there have been equally important advances in our understanding of the inflammatory systems of the periodontal tissues, their control, and how inflammation may contribute both to the development of dysbiosis and, in a deregulated state, the destructive disease process. One can therefore speculate that the inflammatory response and the periodontal microbiome are in a bidirectional balance in oral health and a bidirectional imbalance in periodontitis. However, despite these clear insights into both sides of the host/microbe balance in periodontal disease, there remain several unresolved issues concerning the role of the microbiota in disease. These include, but are not limited to, the factors which determine progression from gingivitis to periodontitis in a proportion of the population, whether dysbiosis causes disease or results from disease, and the molecular details of the microbial stimulus responsible for driving the destructive inflammatory response. Further progress in resolving these issues may provide significant benefit to diagnosis, treatment, and prevention.

Pro-resolving mediators in the regulation of periodontal disease

Periodontitis is an inflammatory disease of the supporting structures of the dentition that is initiated by bacteria that form a biofilm on the surface of the teeth. The pathogenesis of the disease is a result of complex interactions between the biofilm and the host response that results in dysbiosis of the microbiome and dysregulation of the inflammatory response. Current data suggest that the excess inflammation associated with periodontitis is due to a failure of resolution of inflammation pathways. In this review, the relationship between inflammation and microbial dysbiosis is examined in the context of pro-inflammation and pro-resolution mediators and their ability to modify the course of disease. The impact of local oral inflammation on systemic inflammation and the relationship of periodontitis to other inflammatory diseases, including type 2 diabetes and cardiovascular disease is reviewed. Active resolvers of inflammation, including the lipoxins and resolvins, show great promise as therapeutics for the treatment of periodontitis and other inflammatory diseases.

Role of systemic and local administration of selective inhibitors of cyclo-oxygenase 1 and 2 in an experimental model of periodontal disease in rats

BACKGROUND AND OBJECTIVE

Periodontal disease is an inflammatory condition of tooth-supporting tissues. Arachidonic acid metabolites have been implicated in development of periodontal disease, especially those derived from the cyclo-oxygenase (COX) pathway. This study investigated the role of inhibitors of cyclo-oxygenases (COX-1 and COX-2) in a model of periodontal disease in rats.

MATERIAL AND METHODS

A ligature was placed around the molar of rats. Losses of fiber attachment and of alveolar bone were measured morphometrically in histologically prepared sections. Infiltration of cells into gingival tissue surrounding the ligated tooth was also determined.

RESULTS

Systemic and local administration of non-selective and selective COX-2 inhibitors, preventively, resulted in significant reduction of the losses of fiber attachment and alveolar bone, as well as decreased leukocyte numbers in gingival tissue. Preventive selective inhibition of COX-1 was as effective as COX-2 inhibition in reducing local fiber attachment loss and cell migration, but did not prevent alveolar bone loss.

CONCLUSION

Our results provide evidence for participation of COX-1 and COX-2 in early stages of periodontal disease in rats. Furthermore, local administration of COX inhibitors reduced the signs of periodontal disease to the same extent as systemic treatment. Therapeutic approaches incorporating locally delivered anti-inflammatory drugs could be of benefit for patients suffering from periodontal disease.

Pilot study on n-3 polyunsaturated fatty acids in the treatment of human experimental gingivitis

The anti-inflammatory effect of n-3 PUFA on the gingivae has already been demonstrated in animal models. The aim of this double-blind, randomized pilot study versus placebo is to evaluate this action in human experimentally-induced gingivitis. For 14 days (D0-D14), 37 healthy volunteers practised intensive oral hygiene, then abstained from brushing their teeth for 21 days (D14 to D35). On D28, the patients were randomized into 2 groups: 18 received the drug (fish oil: 30% n-3 PUFA) and 19 received the placebo (olive oil containing only 1% of n-3 PUFA) at a daily dosage of 6 g (i.e., 1.8 g of n-3 PUFA) 3x for 8 days (D28-D35). The plaque (PI), gingival (GI) and papillary bleeding (PBI) indices were measured on D14, D28 and D35. On D28 and D35, 10 volunteers underwent removal of an inter-dental vestibular papilla, between the 1st and the 2nd superior premolars, to measure out arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA). A gingival biopsy was also taken in another 11 patients, to assay prostaglandin E2 (PGE2) and leukotriene B4 (LTB4). The clinical results of the trial demonstrated, in particular, a significant reduction of GI in the treated group (p < 0.05, Student t-test), but no significant difference between the groups. The biochemical results showed that EPA, DHA and DPA were found in the cells sampled, at higher levels in the subjects taking the drug, with a significant difference for EPA between the 2 groups (p < 0.05, Student t-test). The levels of AA, PGE2 and LTB4 are reduced in the experimental group and increased in the control group, with no significant difference. The LTB4 levels decreased but this difference just failed to reach significance (p = 0.09. Student t-test). This human experimental gingivitis study demonstrated that n-3 PUFA induced a tendency towards reduced inflammation but it was not possible to conclude significant efficacy.

The effect of systemic ibuprofen on gingival inflammation in humans

This clinical trial investigated the influence of short-term ibuprofen therapy on the early phase of the treatment of adult chronic periodontitis. The subjects were 17 patients in good general health referred for specialist periodontal treatment, having moderate chronic adult periodontitis. A series of assessments were made every 2 weeks over an 8-week period, including evaluations of oral hygiene, gingival inflammation and probing pocket depths. All participants received oral hygiene instruction, and following baseline examinations, had half the dentition, chosen at random, treated by scaling and root planing. The patients were randomly distributed into 2 groups, a test group receiving a 14-day course of 800 mg ibuprofen daily, in 4 divided doses, and a control group who did not receive any drug regime. At the 2-week assessment following the drug regime, significantly greater reduction in gingival bleeding, colour and pocketing was detected in the test compared with the control group. The beneficial effects were less evident thereafter. Although clinical application of the regime used in this study would not be justified by these results, further research into anti-inflammatory agents as an adjunct in the treatment of periodontal diseases could be considered, in the light of the beneficial effect on gingivitis in the early phase of periodontal treatment reported.

Leukotrienes: their possible role in pulpal and periapical diseases

Leukotrienes play an important role in inflammation and its sequelae such as pain, swelling, and bone resorption. This review covers, their history, structure, synthesis, metabolism, biological effects, inhibitors, antagonists, and their possible role in pathogenesis of pulpal and periapical disease.

Periodontal alterations in patients with pemphigus vulgaris taking steroids. A biannual assessment

Periodontal health parameters and salivary cortisol were studied in 19 adult pemphigus vulgaris patients on chronic steroid therapy. The patient population was divided into non-medicated and medicated subjects at intake into the study. A significant difference between the 2 examinations, performed at an interval of 8.73 months +/- 4.35, was found in bleeding index (p less than 0.000 and p less than 0.04, respectively) and gingival recession (p less than 0.000 and p less than 0.009) in both groups. No changes occurred in alveolar bone height. Steroid therapy altered the bleeding index (R = 0.60 and R = 0.80) and gingival recession (R = 0.87 and 0.91) in a dose-related manner, and induced low salivary cortisol. The findings of this study would suggest suppression of the host inflammatory reaction, resulting in an alleged healthy clinical appearance of the periodontium.

Inhibition of human periodontal prostaglandin E2 synthesis with selected agents

Considerable evidence has demonstrated the importance of PGE2 synthesis in the pathogenesis of periodontal disease. Although various cyclooxygenase inhibitors have been known to block periodontal PGE2 synthesis and prevent disease progression in animal models, there are few reports comparing relative efficacies of various inhibitors of arachidonic acid (ARA) metabolism. We have developed a sensitive in vitro assay to measure PGE2 synthesis in periodontal tissues. The apparent IC50 values (i.e. the concentration of drug which causes 50% inhibition of maximum PGE2 synthesis) have been determined for a series of arachidonic acid analogues as well as competitive and non-competitive cyclooxygenase inhibitors. Periodontal tissue homogenates were incubated in the presence of 3H-arachidonic acid for 45 min at 37 degrees C. Inhibitors were tested at 10(-10)-10(-4) M and at zero concentration to measure conversion of 3H-arachidonate to 3H-PGE2. Log or half log dilutions of inhibitors were tested in triplicate for each assay. Radiolabeled PGE2 was extracted from homogenates, purified by reverse phase chromatography and quantitated by double antibody capture. RIA was performed on each homogenate to determine the amount of endogenous unlabeled PGE2 present in the sample to correct for antibody capture recovery. The apparent IC50 values were determined for each drug by averaging two or more replicate assays. Specific total enzymatic activity of periodontal tissue homogenates was typically 5-11 pg PGE2/min/mg tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Periodontal conditions in adults with rheumatoid arthritis

Periodontal conditions among an adult population of 161 dentate patients with rheumatoid arthritis (RA) were compared with those of an age and sex-matched random sample of non-rheumatic subjects. The number of teeth and prevalence of dental plaque, calculus, gingivitis, and deepened periodontal pockets were recorded. Alveolar bone breakdown and the distribution of subjects according to severity of periodontal disease were also registered. There was a tendency towards better periodontal conditions among RA-patients, severe periodontal breakdown occurring less frequently among RA-patients (12%) than among the controls (16%). The RA-patients had less plaque and calculus than the control group, a finding which could indicate a difference in periodontal care.

Rat ovarian prostaglandin levels and ovulation as indicators of the strength of non-steroidal anti-inflammatory drugs

Immature Wistar rats were treated with pregnant mare's serum gonadotropin and human chorionic gonadotropin to induce ovulation. The non-steroidal anti-inflammatory drugs indomethacin, diclofenac, flurbiprofen, and phenylbutazone inhibited both the ovulation rate and the normal increase in ovarian prostaglandin E during ovulation. Tolmetin, ibuprofen, and aspirin did not have any significant effect. There was a significant correlation between the ovulation rate and the level of ovarian prostaglandin E following treatment with these drugs. When indomethacin was given in graded doses, there was also a correlation between ovulation rate and the dose-dependent inhibition of ovarian prostaglandin E.

Drugs and the periodontium

The periodontium and periodontal disease activity can be affected by systemic drug therapy. Many drugs can have an adverse effect on the periodontium, i.e., gingival hyperplasia. Alternatively, some drugs can modify the inflammatory and immunological responses of the periodontal tissues to bacterial plaque. The aim of this review is to evaluate the effects of drug therapy on the periodontium and periodontal disease activity, and where possible, to relate such changes to the pharmacodynamics of the drugs considered. Drugs which have been reported to affect the periodontium can be categorised as follows: anti-epileptics, immunosuppressants, corticosteroids, non-steroidal anti-inflammatory drugs and hormones. Those drugs whose pharmacodynamics are clearly established and which affect the rate of periodontal disease activity, may provide information on the mechanisms of periodontal destruction. Finally, the mechanisms of drug-induced gingival hyperplasia (overgrowth) are discussed in relationship to the drugs' pharmacodynamics and pharmacokinetics.

The osteoclast and periodontitis

The osteoclast may play an important rŏle in the variable rate of osseous destruction seen in periodontitis. Current understanding of various aspects of the osteoclast may help explain this fact. This review paper will first look at two theories of cell origin of the osteoclast: the multipotential osteoprogenitor cell theory and the hemopoietic stem cell theory. Next, ultrastructural features characteristic to the cell such as the ruffled border, clear zone, and lysosomal system, will be discussed. Thirdly, current and proposed theories on the actual mechanism of bone degradation are considered. This includes the one-cell theory and the two-cell theory. Finally, elements which activate the osteoclast are enumerated and their delicate interplay is outlined. In the context of this information, pathways found in the periodontal lesion (microbial agents, inflammatory cells and their products) which attract and activate elements of the osteoclastic system are discussed.