B. Poligone et As. Baldwin, Positive and negative regulation of NF-kappa B by COX-2-Roles of differentprostaglandins, J BIOL CHEM, 276(42), 2001, pp. 38658-38664
The prostaglandin H synthases (PGHS) catalyze the conversion of arachidonic
acid to prostaglandin H-2, the committed step in prostanoid synthesis. Two
forms of PGHS exist, PGHS-1 (COX-1) and PGHS-2 (COX-2). The gene encoding
the latter form is known to be inducible by a number of stimuli including s
everal inflammatory mediators. Recent evidence indicates that the inducible
cyclooxygenase may have both pro- and anti-inflammatory properties through
the generation of different prostaglandins. Previous reports indicate that
the transcription factor NF-kappaB can function upstream of COX-2 to contr
ol transcription of this gene and that the cyclopentenone prostaglandins ca
n inhibit NF-kappaB activation via the inhibition of the I kappaB kinase. T
hus, it is suggested that cyclopentenones feed back to inhibit continued nu
clear accumulation of NF-kappaB. In this report we demonstrate COX-2 expres
sion inhibits nuclear translocation of NF-kappaB, and we confirm that the c
yclopentenone prostaglandins inhibit NF-kappaB. In addition, we show that p
rostaglandin E-2 and its analogs promote the inherent transcriptional activ
ity of the p65/RelA subunit of NF-kappaB in a manner independent of induced
nuclear accumulation. Consistent with this evidence, prostaglandin E2 stro
ngly synergizes with the inflammatory cytokine tumor necrosis factor-a to p
romote NF-kappaB-dependent transcription and gene expression. The data prov
ide a molecular rationale to explain both the pro- and anti-inflammatory na
ture of COX-2.