Objective—To determine the effects of prostaglandin
E2 (PGE2) on recombinant equine interleukin (IL)-1β-stimulated expression of matrix metalloproteinases
(MMP 1, MMP 3, MMP 13) and tissue inhibitor of
matrix metalloproteinase 1 (TIMP 1) in vitro.
Sample Population—Cultured equine chondrocytes.
Procedure—Stationary monolayers of first-passage
chondrocytes were exposed to graduated concentrations
of PGE2 with or without a subsaturating dose
(50 pg/ml) of recombinant equine IL-1β (reIL-1β) to
induce expression of MMP 1, MMP 3, MMP 13, and
TIMP 1, followed by RNA isolation and northern blotting.
In subsequent experiments, gene expression
was similarly quantified from mRNA isolated from cultures
pretreated with phenylbutazone to quench
endogenous PGE2 synthesis, followed by exposure to
reIL-1β and exogenous PGE2 (5 mg/ml) with appropriate
Results—Exogenous PGE2 (10 mg/ml) significantly
reduced reIL-1β-induced expression of MMP 1,
MMP 3, MMP 13, and TIMP 1. Abrogation of
cytokine induction with this dose of PGE2 was comparable
to that for dexamethasone (10–5M) control.
Similarly, pretreatment with phenylbutazone, followed
by exposure to reIL-1β and PGE2 (5 mg/ml),
was associated with a reduced expression of the
genes of interest, an effect that was significant for
MMP 1, MMP 13, and TIMP 1.
Conclusions and Clinical Relevance—The MMP
and TIMP 1 are important mediators in the pathophysiologic
events in osteoarthritis. The potential for
physiologically relevant regulation of expression of
these genes by PGE2 is a consideration in the use of
drugs that inhibit prostanoid synthesis in the treatment
of equine arthropathies. (Am J Vet Res
Objective—To determine the effects of recombinant
equine interleukin -1β (reIL-1β) and 4 anti-inflammatory
compounds on the expression and activity of
cyclooxygenase (COX)-2 in cultured equine chondrocytes.
Sample Population—Articular cartilage from 9
young adult horses.
Procedure—Reverse transcriptase-polymerase chain
reaction methods were used to amplify a portion of
equine COX-2 to prepare a cDNA probe. Northern blot
analysis was used to quantify the expression of
COX-2 in first-passage cultures of equine articular
chondrocytes propagated in media containing dexamethasone
(DEX), phenylbutazone (PBZ), polysulfated
glycosaminoglycan, and hyaluronan, each at concentrations
of 10 and 100 µg/ml and each with or without
reIL-1β. A commercial immunoassay was used to
determine prostaglandin E2 (PGE2) concentrations in
conditioned medium of similarly treated cells to quantify
Results—Addition of reIL-1β increased the expression
of COX-2 in a dose-dependent manner, which was
paralleled by an increased concentration of PGE2 in
culture medium. Concentration of PGE2 in spent
medium from reIL-1β-treated chondrocytes was significantly
reduced by DEX and PBZ; however, only
DEX significantly reduced gene expression of COX-2.
Conclusions and Clinical Relevance—Prostaglandin
E2 is considered to be an important mediator in the
pathophysiologic processes of arthritis, and cultured
chondrocytes respond to interleukin-1 with enhanced
expression and activity of COX-2. Palliative relief in
affected horses is probably attributable, in part, to
inhibition of PGE2 synthesis; however, analysis of
these data suggests that of the 4 compounds tested,
only DEX affects pretranslational regulation of the
COX-2 gene in cultured equine chondrocytes.
(Am J Vet Res 2002;63:1134–1139)