The effect of non-steroidal anti-inflammatory drugs on the metabolism of 14C-arachidonic acid by human gingival tissue in vitro

Prostaglandins: biphasic dose responses

Biphasic dose responses induced by prostaglandins are documented and assessed with respect to quantitative features of their dose-response functions, mechanistic foundation, and biological generalizability. Biphasic responses were seen for multiple endpoints, including DNA synthesis, neutrophil migration, corticosterone production, fibroblast proliferation, and other parameters. In addition, numerous nonsteroidal antiinflammatory agents and other drugs alter prostaglandin concentrations and/or transport in a biphasic dose- response manner. These findings have considerable implications for the understanding of basic biological regulatory processes as well as clinical practices.

Cyclooxygenase-2-dependent prostaglandin production by peripheral blood monocytes stimulated with lipopolysaccharides isolated from periodontopathogenic bacteria

BACKGROUND

Prostaglandin E2 (PGE2) plays important roles in the pathogenesis of periodontal disease. Recent studies have revealed the existence of 2 isozymes of cyclooxygenase (COX), called COX-1 and COX-2. The purpose of the present study was to investigate the contribution of COX-1 and COX-2 to PGE2 production by human peripheral blood monocytes that are stimulated with lipopolysaccharides (LPS) from periodontopathogenic bacteria.

METHODS

LPS were isolated from Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) and Porphyromonas gingivalis (P. gingivalis) by the phenol-water method. Peripheral blood monocytes were stimulated with LPS for the indicated periods, and the levels of PGE2 or interleukin (IL)-1 beta in the culture media were measured by enzyme-linked immunosorbent assay. Expression of COX-1 and -2 proteins was studied by immunocytochemical staining, and COX-2 mRNA expression was examined by Northern blot analysis.

RESULTS

Peripheral blood monocytes stimulated with A. actinomycetemcomitans- or P. gingivalis-LPS produced PGE2 in a time- and dose-dependent manner. Indomethacin, a non-selective COX-1/COX-2 inhibitor, and NS-398, a specific COX-2 inhibitor, completely inhibited PGE2 production. Immunocytochemical staining of COX-1 and COX-2 proteins showed that expression of COX-2 protein was increased in monocytes that were stimulated with A. actinomycetemcomitans- or P. gingivalis-LPS, compared with that in unstimulated monocytes, whereas expression of COX-1 protein was not altered. Northern blot analysis showed that monocytes stimulated with A. actinomycetemcomitans- or P. gingivalis-LPS expressed COX-2 mRNA, while COX-2 mRNA was not detectable in unstimulated cells. Treatment of A. actinomycetemcomitans-LPS-stimulated monocytes with NS-398 induced a significant increase of IL-1 beta production to the same extent as treatment with indomethacin.

CONCLUSIONS

These results suggest that COX-2 is induced in monocytes stimulated with LPS derived from A. actinomycetemcomitans and P. gingivalis and that the COX-2 is primarily responsible for PGE2 production. COX-2 may be pivotal in PGE2 production in periodontal lesions and may be involved in inflammatory responses.

Effects of ketorolac tromethamine mouthrinse (0.1%) on crevicular fluid prostaglandin E2 concentrations in untreated chronic periodontitis

The effects of topical ketorolac tromethamine mouthrinse (0.1%) on gingival crevicular fluid (GCF) prostaglandin E2 (PGE2) concentrations were investigated in a 6-week, randomized, double-blind, placebo-controlled, parallel group, single center study of 42 patients with moderately advanced chronic adult periodontitis. Following screening, GCF was sampled from 6 sites per subject with filter paper strips and PGE2 levels measured using an enzyme immunoassay kit. Only those subjects with mouth median GCF PGE2 concentrations >30 ng/ml entered the rinsing phase. Eligible subjects were allocated placebo rinse in the first 2-week period (days 0 through 14), either ketorolac rinse (test group, n = 21) or placebo rinse (control group, n = 21) in the second 2-week period (days 14 through 28), and placebo rinse in the third 2-week period (days 28 through 42). Full mouth median GCF PGE2 concentrations were calculated for each subject at days 0, 14, 28, and 42, and group means were compared. From day 0 to day 14, no significant changes in GCF PGE2 concentrations were detected in either study group (P > 0.05). Utilizing mean GCF PGE2 concentrations at days 0 and 14 as covariates, no significant differences were observed in adjusted mean PGE2 levels at days 28 and 42 between the study groups (ANCOVA, P > 0.05). A statistically significant increase in GCF PGE2 levels was noted at days 28 and 42 in the placebo group (P < 0.01), but not in the ketorolac group (P > 0.05), when compared to baseline, however. GCF PGE2 levels were further studied in a subset of volunteers (n = 11) during a 12-hour period following first rinsing with mouthrinse (active or placebo) at day 14. GCF was sampled 0, 2, 4, 6, 8, and 12 hours post-rinsing. Mean PGE2 levels were higher in the placebo subgroup than in the ketorolac subgroup, and increased gradually over the 12-hour period in both subgroups. These data indicate that 1) 14 days of rinsing with 0.1% ketorolac mouthrinse controlled the elevation of GCF PGE2 observed in the placebo group but did not actually reduce GCF PGE2 concentrations and 2) changes in GCF PGE2 levels were not detectable in the 12-hour period following first rinsing with ketorolac.

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.

Blocking periodontal disease progression with anti-inflammatory agents

Recent advances in the identification of specific immuno-inflammatory pathways of periodontal disease have encouraged investigators to attempt to modulate some of these host responses in an attempt to slow the periodontal disease process. Some of the best known mediators of these immuno-inflammatory pathways are prostaglandins. The action of prostaglandins can be inhibited through the use of non-steroidal anti-inflammatory drugs (NSAIDs). This review examines research over the last two decades during which the effect of several NSAIDs on the progression of gingival inflammation and alveolar bone loss was explored.

Nonsteroidal antiinflammatory drugs as inhibitors of periodontal disease progression

Recent interest in the control and modulation of periodontal disease has focused on the potential benefits of blocking the host response mechanisms involved in the progression of the disease. In addition to recent advances in the identification and control of etiologic bacteria, investigators have indicated promising results using nonsteroidal antiinflammatory drugs (NSAIDs) as inhibitors of the inflammatory destruction in periodontal disease. This article examines research efforts over the last 20 years describing the role of prostaglandins in periodontal disease and the effect of NSAIDs on the progression of gingival inflammation and alveolar bone loss.

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.

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)

The effect of a topical non-steroidal anti-inflammatory drug on the development of experimental gingivitis in man

24 healthy volunteers abstained from tooth-cleaning for 17 days. Parameters of gingival health were recorded on days 1 and 17. On days 4, 6, 8, 11, 13 and 15, each volunteer randomly received, on a double-blind basis, 100 ml of 10 mM flurbiprofen solution in buffered preservative to one upper quadrant of the mouth. The contralateral quadrant received preservative only. Applications were made using a pulsed jet irrigating system. Gingivitis developed in all patients and there were no significant differences between the treatments for gingival index or pocket probing depths. When gingival health was re-established, 4 volunteers had a further 3 irrigations of flurbiprofen at intervals of 2 days. Plasma levels of flurbiprofen were determined after the 1st and 3rd irrigations. Assays showed that the drug was present in the plasma of all 4 subjects (range 0.2-0.7 micrograms/ml). Gingival health was re-established in 6 further volunteers from the original study. They then abstained from toothbrushing for 17 days, during which one maxillary quadrant was irrigated with the buffered preservative solution. The irrigations were made on the same basis as in the original study. Gingivitis again developed in these quadrants, although when the results were compared to the equivalent data from the first investigation, significantly greater median values for probing pocket depths and gingival indices were found in the latter study. Therefore, it appears that systemic absorption of flurbiprofen may have reduced the severity of the developing inflammatory lesions.

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.

Prostaglandin-related bone resorption in cultured neonatal mouse calvaria: evaluation of biopotency of nonsteroidal anti-inflammatory drugs

The objective of this study was the development of an assay based on suppression of endogenous prostaglandin synthesis in cultured neonatal mouse calvaria for evaluation of the biopotency of nonsteroidal anti-inflammatory drugs in bone. In preliminary trials, osteolytic activity due to spontaneous prostaglandin production over a 72 h culture period was found highly variable, and could not be stabilized by addition of the common precursor arachidonic acid to the culture medium. Eventually, continuous exposure of mouse calvaria to moderate concentrations of thrombin (greater than or equal to 14 U/ml medium) proved to be satisfactory to achieve stable rates of bone resorption through continuous stimulation of prostaglandin synthesis from endogenous sources. Notably, the extent of net calcium release into the medium was highly reproducible in different experiments. As an example for possible applications of the bioassay, the ability of acemetacin to interfere with prostaglandin synthesis in bone, which had not been assessed before, was evaluated in a comparative assay with indomethacin and acetylsalicylic acid. While 1 X 10(-8) M acemetacin appeared to augment thrombin-induced bone resorption, as did 5 X 10(-6) M acetylsalicylic acid, a dose-dependent inhibition of calcium release was observed between 10(-7)-10(-5) M acemetacin. In this respect, the biopotency of indomethacin was 50 times higher than that of acemetacin and exceeded that of acetylsalicylic acid by a factor of more than 2000. These data could be useful for the appraisal of multiple effects of the investigated drugs on prostaglandin-related bone turnover.

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

Prostaglandin (PG) synthetase inhibitors are tissue-selective. Therefore, the action of four nonsteroidal anti-inflammatory drugs (NSAID) was tested against PG synthesis from 14C-arachidonic acid by gingival homogenate. Suprofen and tolmetin sodium did not significantly inhibit PGs at any of the three concentration levels used (10(-7), 10(-5), 10(-3) M), whereas flurbiprofen and zomepirac sodium did significantly inhibit PG formation at millimolar concentration. The results, coupled with our previous study on indomethacin, piroxicam and ibuprofen open the way for future tests of NSAIDs in treatment of gingival inflammation and periodontal disease.