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Cyclooxygenase‐2 Is Upregulated in Inflamed Gingival Tissues
Author(s) -
Morton Rakhi Sinha,
DongariBagtzoglou Anna I.
Publication year - 2001
Publication title -
journal of periodontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.036
H-Index - 156
eISSN - 1943-3670
pISSN - 0022-3492
DOI - 10.1902/jop.2001.72.4.461
Subject(s) - cyclooxygenase , inflammation , immunohistochemistry , downregulation and upregulation , proinflammatory cytokine , prostaglandin e2 , prostaglandin e , medicine , pathology , connective tissue , prostaglandin , western blot , in vivo , macrophage , immunology , chemistry , in vitro , biology , enzyme , biochemistry , microbiology and biotechnology , gene
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 E 2 (PGE 2 ) 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)‐1β 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‐1β challenge and was accompanied by a sustained PGE 2 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 PGE 2 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‐1β and bacterial constituents may be responsible for the enhanced COX‐2 expression and PGE 2 synthesis in vivo. J Periodontol 2001;72:461‐469.