Cyclooxygenase-2 is upregulated in inflamed gingival tissues.
BACKGROUND
Increased release of prostaglandins (PG) within periodontal tissues is considered to play a pathogenetic role during periodontal disease progression. The rate-limiting step in the formation of PG from arachidonic acid is catalyzed by cyclooxygenase (COX). Currently there are 2 known isoforms of the enzyme. COX-1 is constitutively expressed in various tissues whereas COX-2 is an inducible enzyme believed to be responsible for PG synthesis at sites of inflammation. The purpose of this study was to compare COX-2 expression in inflamed and healthy human gingiva and further explore some of the pathogenetic mechanisms which may lead to elevated COX-2 expression in vivo.


METHODS
Thirty-two gingival biopsies were obtained during routine oral surgical procedures and were processed histologically using hematoxylin and eosin to determine the degree of inflammation. Of these biopsies, 7 with low and 7 with high histological levels of inflammation were further processed immunohistochemically in order to assess the levels of COX-2 expression in situ. To explore some potential mechanisms of COX-2 upregulation, gingival connective tissue primary cell cultures were established and challenged with periodontal bacteria or proinflammatory cytokines in vitro. The levels of COX-2 expression were analyzed by Western blot of cell lysates. COX-2 activity was assessed by quantifying prostaglandin E2 (PGE2) levels in culture supernatants by competitive EIA.


RESULTS
We have shown by immunohistochemistry that COX-2 expression was significantly higher (P < 0.01) in tissues with higher levels of inflammatory infiltrates. Expression of COX-2 was detected in gingival epithelium, endothelial cells as well as cells with fibroblast morphology. In vitro studies indicated that gingival fibroblasts (GF) did not express COX-2 constitutively. However, when these cells were challenged with interleukin (IL)-1 beta or bacterial cells (A. actinomycetemcomitans JP2 or B. forsythus ATCC 43037), COX-2 expression as well as COX-2 activity were upregulated. COX-2 expression was upregulated as early as 2 hours post IL-1 beta challenge and was accompanied by a sustained PGE2 release in the culture supernatants. Cyclosporin A (CsA) did not inhibit COX-2 expression induced by bacterial challenge. In contrast, NS-398, a selective inhibitor of COX-2 activity, almost completely abolished PGE2 synthesis by these cells in response to bacterial or cytokine challenge.


CONCLUSIONS
We conclude that COX-2 expression is significantly upregulated in inflamed periodontal tissues. Both inflammatory cytokines such as IL-1 beta and bacterial constituents may be responsible for the enhanced COX-2 expression and PGE2 synthesis in vivo.
Morton
R S
RS
Division of Oral Biology, Columbia University, School of Dental and Oral Surgery, New York, NY, USA.
Dongari-Bagtzoglou
A I
AI
D016976:Aggregatibacter actinomycetemcomitans / Q000502:physiology; D001439:Bacteroides / Q000502:physiology; D001706:Biopsy; D015153:Blotting, Western; D002478:Cells, Cultured; D004396:Coloring Agents; D003239:Connective Tissue Cells / Q000201:enzymology; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D016572:Cyclosporine / Q000187:drug effects; D015232:Dinoprostone / Q000032:analysis; D004727:Endothelium / Q000201:enzymology / Q000473:pathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004801:Eosine Yellowish-(YS); D004848:Epithelium / Q000201:enzymology; D005347:Fibroblasts / Q000201:enzymology; D005456:Fluorescent Dyes; D015870:Gene Expression; D005881:Gingiva / Q000201:enzymology; D005891:Gingivitis / Q000201:enzymology*; D006416:Hematoxylin; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins; D009578:Nitrobenzenes / Q000494:pharmacology; D010544:Peroxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D013223:Statistics as Topic; D018709:Statistics, Nonparametric; D013449:Sulfonamides / Q000494:pharmacology; D015854:Up-Regulation
D004396:Coloring Agents; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007375:Interleukin-1; D007527:Isoenzymes; D008565:Membrane Proteins; D009578:Nitrobenzenes; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D016572:Cyclosporine; D010544:Peroxidases; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D004801:Eosine Yellowish-(YS); D006416:Hematoxylin