Effects of anti-arthritis preparations on gene expression and enzyme activity of cyclooxygenase-2 in cultured equine chondrocytes

Jayne T. Tung Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.

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Patrick J. Venta Departments of Small Animal Clinical Sciences, Microbiology and Molecular Genetics College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.

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Susan W. Eberhart Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.

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Vilma Yuzbasiyan-Gurkan Departments of Small Animal Clinical Sciences, Microbiology and Molecular Genetics, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.

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Lee Alexander Departments of Small Animal Clinical Sciences, Microbiology and Molecular Genetics, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.

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John P. Caron Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.

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 DVM, MVSc

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Abstract

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 COX-2 activity.

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)

Abstract

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 COX-2 activity.

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)

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