Cycooxygenase-2-dependent prostaglandin production by peripheral blood monocytes stimulated with lipopolysaccharides isolated from periodontopathogenic bacteria
K. Noguchi et al., Cycooxygenase-2-dependent prostaglandin production by peripheral blood monocytes stimulated with lipopolysaccharides isolated from periodontopathogenic bacteria, J PERIODONT, 71(10), 2000, pp. 1575-1582
Background: Prostaglandin E-2 (PGE(2)) plays important roles in the pathoge
nesis 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 t
o PGE(2) production by human peripheral blood monocytes that are stimulated
with lipopolysaccharides (LPS) from periodontopathogenic bacteria.
Methods: LPS were isolated from Actinobacillus actinomycetemcomitans (A. ac
tinomycetemcomitans) and Porphyromonas gingivalis (P. gingivalis) by the ph
enol-water method. Peripheral blood monocytes were stimulated with LPS for
the indicated periods, and the levels of PGE(2) or interleukin (IL)-1 beta
in the culture media were measured by enzyme-linked immunosorbent assay. Ex
pression of COX-1 and -2 proteins was studied by immunocytochemical stainin
g, and COX-2 mRNA expression was examined by Northern blot analysis.
Results: Peripheral blood monocytes stimulated with A. actinomycetemcomitan
s- or P. gingivalis-LPS produced PGE(2) in a time- and dose-dependent manne
r. Indomethacin, a non-selective COX-1/COX-2 inhibitor, and NS-398, a speci
fic COX-2 inhibitor, completely inhibited PGE(2) production. Immunocytochem
ical staining of COX-I and COX-2 proteins showed that expression of COX-2 p
rotein was increased in monocytes that were stimulated with A. actinomycete
mcomitans- or P. gingivalis-LPS, compared with that in unstimulated monocyt
es, whereas expression of COX-1 protein was not altered. Northern blot anal
ysis 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-IP production to
the same extent as treatment with indomethacin.
Conclusions: These results suggest that COX-2 is induced in monocytes stimu
lated with LPS derived from A. actinomycetemcomitans and P. gingivalis and
that the COX-2 is primarily responsible for PGE(2) production. COX-2 may be
pivotal in PGE(2) production in periodontal lesions and may be involved in
inflammatory responses.