Recombinant equine interleukin-1beta induces putative mediators of articular cartilage degradation in equine chondrocytes.

Interleukin-1 is considered a central mediator of cartilage loss in osteoarthritis in several species, however an equine recombinant form of this cytokine is not readily available for in vitro use in equine osteoarthritis research. Equine recombinant interleukin-1beta was cloned and expressed and its effects on the expression and activity of selected chondrocytic proteins implicated in cartilage matrix degradation were characterized. Reverse transcriptase polymerase chain reaction methods were used to amplify the entire coding region of the equine IL-1beta mRNA, which was cloned into an expression vector, expressed in E. coli, and purified using a Ni2+ chromatographic method. The effects of the recombinant peptide on chondrocyte gene expression were determined by Northern blotting using RNA from equine chondrocyte cultures hybridized to probes for matrix metalloproteinases (MMP 1, MMP 3, MMP 13), tissue inhibitor of matrix metalloproteinases 1 (TIMP 1) and cyclooxygenase 2 (COX 2). Effects on selected mediators of cartilage degradation (nitrite concentrations and MMP activity) were determined using conditioned medium from reIL-1beta-treated equine cartilage explant cultures. A recombinant peptide of approximately 21 kd was obtained. Northern blotting analyses revealed a marked up-regulation of expression of all MMPs, TIMP 1, and COX 2 in mRNA from treated chondrocytes. Furthermore, cartilage explants exposed to reIL-1beta had augmented collagenase/gelatinase and stromelysin activities as well as increased concentration of nitrite in conditioned media. The development of a biologically active, species-specific IL-1beta provides a valuable tool in the study of osteoarthritis pathophysiology and its treatment in horses.

Inducible nitric oxide expression in equine articular chondrocytes: effects of antiinflammatory compounds.

OBJECTIVE: To determine the effects of recombinant equine IL-1beta and a number of antiinflammatory compounds on the expression and activity of inducible nitric oxide synthase (iNOS) in cultured equine chondrocytes. DESIGN: RT-PCR methods were used to amplify a portion of the equine iNOS message to prepare an RNA probe. Northern blot analysis was used to quantify the expression of iNOS in first passage cultures of equine articular chondrocytes propagated in the presence or absence of recombinant equine interleukin-1beta (reIL-1beta), dexamethasone (DEX), polysulfated glycosaminoglycan (PSGAG), hyaluronan (HA), and phenylbutazone (PBZ), each at concentrations of 10 and 100 microg/ml. Nitrite concentrations in conditioned media of similarly treated cells were used to quantify iNOS activity. RESULTS: Recombinant equine IL-1beta increased the expression of iNOS in a dose-dependent manner. This result was paralleled by an increased concentration of nitrite in the culture media of reIL-1beta-treated cells. DEX and PSGAG significantly reduced iNOS gene expression and media supernatant nitrite concentrations in cytokine-stimulated cultures. HA and PBZ had no consistent effect on the expression of iNOS and did not significantly influence nitrite content of conditioned media. CONCLUSIONS: NO is considered an important mediator in the pathophysiologic processes of arthritis and an inducible NOS is expressed by equine chondrocytes. Pre-translational regulation of the iNOS gene by DEX and PSGAG appears to contribute to the cartilage-sparing properties of these compounds.