Effects of glucocorticoids and interleukin-1 beta on expression and activity of aggrecanases in equine chondrocytes.

This study explores the effects of certain substances—interleukin-1 beta and glucocorticoids—on the degradation of cartilage in horses. The researchers found that both substances can increase the activity of aggrecanase, an enzyme involved in cartilage breakdown, which has significant implications for treatment options for cartilage-related conditions.

Methodology

• The researchers extracted cartilage from 24 equine cadavers that were free of sepsis and musculoskeletal disease.
• They studied the effects of interleukin-1 beta, interleukin-1 beta combined with glucocorticoids (dexamethasone and triamcinolone), and glucocorticoids on their own on the degradation of articular and nasal cartilage in horses.
• They observed the process of degradation by monitoring the release of glycosaminoglycan (GAG), a substance found in the cartilage, and the content of this substance in the cartilage itself.
• They followed the cleaving of a component known as the interglobular domain at Glu373-Ala374, which occurs due to aggrecanase activity, using western blot analysis and ELISAs – common laboratory techniques to identify specific molecules.
• They quantified the mRNA concentrations of several markers (MMP-3, MMP-13, ADAMTS4, and ADAMTS5) that indicate the process of degradation. This was performed on cartilage explants via real-time reverse transcriptase PCR assay and on cell culture using northern blot analysis.

Results

• Interleukin-1 beta resulted in elevated GAG release and aggrecanase activity. MMP-3, MMP-13, and ADAMTS4 mRNAs were notably upregulated with IL-1 beta, whereas ADAMTS5 mRNA was increased.
• ADAMTS5 mRNA was increased less considerably than the others, suggesting that both ADAMTS4 and ADAMTS5 are involved in the breakdown of cartilage under the influence of cytokine stimulation.
• Even though glucocorticoids resulted in downregulation of MMP-3 and MMP-13 mRNAs, contrary to expectations, GAG degradation continued unaltered.
• An unexpected increase in aggrecanase activity was also observed despite the downregulation of ADAMTS4 mRNA, suggesting that ADAMTS5 may play a major role here.

Conclusions

• The research indicates that MMP-3, MMP-13, and ADAMTS4 are regulated differently than ADAMTS5. The findings imply that glucocorticoids can heighten aggrecanase activity, even with the down-regulation of ADAMTS4 mRNA, which suggests a prominent role of ADAMTS5.
• The impact of glucocorticoids on aggrecanase activity has critical implications in terms of treatment of cartilage-related conditions, since these substances are often used as anti-inflammatory medication.