Prostaglandin production via induction of cyclooxygenase-2 by human gingival fibroblasts stimulated with lipopolysaccharides

The purpose of the present study was to investigate the involvement of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in PGE(2) production by human gingival fibroblasts stimulated with lipopolysaccharides (LPS) from periodondopathogenic bacteria. LPS were isolated from Porphyromonas gingivalis (P. gingivalis), Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) and Eschericia coli (E. coli) by the phenol-water procedure. The three LPS preparations produced PGE(2) up to 48 h in a time-dependent manner in human gingival fibroblasts. P. gingivalis-LPS was the most potent stimulator of PGE(2) production and, to a lesser extent, A. actinomycetemcomitans- and E. coli-LPS. Treatment of the cells with indomethacin, a non selective COX-1/COX-2 inhibitor and NS-398, a selective COX-2 inhibitor, completely depressed PGE, production. Treatment of dexamethasone, known to inhibit COX-2 expression, also significantly prevented PGE(2) production. Immunohistochemical staining of COX-2 protein demonstrated that expression of COX-2 protein was increased at 24 h after P. gingivalis-LPS stimulation, while expression of COX-1 protein was not affected by P. gingivalis-LPS. In order to investigate the regulation of PGE(2) production. P. gingivalis-LPS-stimulated cells were treated with herbimycin A and genistein, both inhibitors of tyrosine kinases. Both the inhibitors significantly inhibited PGE(2) production. Herbimycin A treatment depressed expression of COX-2 protein. These data suggest that human gingival fibroblasts stimulated with LPS from periodontopathogenic bacteria mainly produce PGE(2) not by COX-1, but by COX-2, induction of which may be regulated by tyrosine kinase and that the produced PGE(2) may be involved in the pathogenesis of periodontal diseases.