Transcriptional and proteolytic regulation of the insulin-like growth factor-I system of equine articular chondrocytes by recombinant equine interleukin-1beta.
Abstract: Interleukin-1 (IL-1) and insulin-like growth factor-I (IGF-I), which have opposing effects on matrix metabolism within articular cartilage, are thought to play prominent roles in the pathogenesis of osteoarthritis. To better understand the link between these anabolic (IGF-I) and catabolic (IL-1) stimuli, we examined exogenous IL-1 regulation of the IGF-I signaling system of articular chondrocytes (ACs). Equine ACs from non-arthritic stifle joints were expanded in monolayer culture, encapsulated for 10 days in alginate beads, and stimulated as high-density monolayers with recombinant equine IL-1beta (0, 1, 10 ng/ml) for 48 h. IL-1beta enhanced expression of IGF-IR levels, as determined by both [125I]-IGF-I binding studies and Western blotting, while reducing the concentration of endogenous IGF-I detected in conditioned media by radioimmunoassay. Western ligand blotting revealed that chondrocytes primarily secreted IGF binding proteins (IGFBPs) with molecular weights of 28-30 and 32-34 kDa, which were identified as IGFBPs 5 and 2, respectively, and that IL-1beta treatment diminished IGFBP-2, the prominent homolog in conditioned media. Northern blot analysis suggested IL-1beta regulation of IGF-I and, to some extent, IGF-IR was mediated by transcription; however, the cytokine did not affect IGFBP-2 expression. To test for evidence of proteolysis by matrix metalloproteinases (MMPs), additional cultures were co-incubated with inhibitors for MMPs 2/9, 3, and 8. IGFBP-2 suppression was partially reversed by gelatinase (MMP-2/9) inhibition. In summary, these findings further delineate the role of IL-1 as a key regulator of the IGF-I system within articular cartilage, demonstrating that regulation occurs through both direct (transcriptional) and indirect (proteolytic) mechanisms.
Copyright 2006 Wiley-Liss, Inc.
Publication Date: 2006-08-10 PubMed ID: 16897751DOI: 10.1002/jcp.20762Google Scholar: Lookup
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- Journal Article
- Research Support
- N.I.H.
- Extramural
Summary
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The study investigates the interaction of Interleukin-1 (IL-1) and insulin-like growth factor-I (IGF-I), which are believed to play significant roles in the development of osteoarthritis, on the cells of the horse’s cartilage. The research reveals that addition of IL-1 enhanced levels of IGF-I receptor expression while reducing the concentration of IGF-I, existing originally within the system, and demonstrated both direct and indirect modes of regulation.
About Interleukin-1 and Insulin-Like Growth Factor-I
- Interleukin-1 (IL-1) and insulin-like growth factor-I (IGF-I) are significant due to their opposing effects on matrix metabolism within articular cartilage, making them prime candidates in the research of osteoarthritis.
- IGF-I is anabolic (constructive metabolism) in nature promoting growth and repair processes while IL-1 is catabolic (destructive metabolism) breaking down substances within the body.
Objective and Methodology of the Study
- The study aimed to examine how exogenous (originating from outside the organism) IL-1 regulates the IGF-I signaling system in the horse’s cartilage cells (articular chondrocytes).
- The research used equine (horse’s) articular chondrocytes, obtained from non-arthritic joints and grown in a lab environment for a specific period.
- The researchers stimulated these cells with varied concentrations of recombinant equine IL-1beta (produced through genetic engineering) for a set duration.
Findings of the Study
- IL-1beta amplified the expression of IGF-I receptor levels, as observed through binding studies and Western blotting (a technique to detect certain proteins in a given sample).
- At the same time, IL-1beta decreased the concentration of inherent IGF-I as detected in conditioned media (media that have been modified based on cellular activity) by radioimmunoassay (a technique used to measure the concentration of antigens).
- IL-1beta treatment also had a definite effect on the two main types of IGF binding proteins (IGFBPs) – 5 and 2 – that are secreted by the cartilage cells, with the latter being the most prominent in conditioned media.
- Northern blot analysis (a method to detect RNA molecules) suggested that IL-1beta’s regulation of IGF-I was largely through transcriptional regulation (the first step of gene expression).
- Additional experiments involving matrix metalloproteinases (MMPs), enzymes that break down proteins, showed that suppression of IGFBP-2 (binding protein) could be partially reversed upon the inhibition of certain MMPs.
Conclusion
- The researchers conclude that IL-1 is a vital regulator of the IGF-I system within articular cartilage.
- They demonstrated that IL-1’s regulation happens via both direct (transcriptional) and indirect (proteolytic) methods.
Cite This Article
APA
Porter RM, Akers RM, Howard RD, Forsten-Williams K.
(2006).
Transcriptional and proteolytic regulation of the insulin-like growth factor-I system of equine articular chondrocytes by recombinant equine interleukin-1beta.
J Cell Physiol, 209(2), 542-550.
https://doi.org/10.1002/jcp.20762 Publication
Researcher Affiliations
- Department of Chemical Engineering, Virginia Polytechnic Institute & State University, Blacksburg, Virginia 24061-0211, USA.
MeSH Terms
- Animals
- Cartilage, Articular / metabolism
- Cells, Cultured
- Chondrocytes / cytology
- Chondrocytes / metabolism
- Culture Media, Conditioned
- Gene Expression Regulation / drug effects
- Horses / metabolism
- Insulin-Like Growth Factor Binding Protein 2 / metabolism
- Insulin-Like Growth Factor Binding Protein 3 / metabolism
- Insulin-Like Growth Factor I / metabolism
- Interleukin-1 / pharmacology
- Matrix Metalloproteinase Inhibitors
- Models, Biological
- Protein Processing, Post-Translational
- Receptor, IGF Type 1 / metabolism
- Transcription, Genetic / drug effects
Grant Funding
- ARO46414 / PHS HHS
Citations
This article has been cited 1 times.- Wen Y, Li J, Tan Y, Qin J, Xie X, Wang L, Mei Q, Wang H, Magdalou J, Chen L. Angelica Sinensis polysaccharides stimulated UDP-sugar synthase genes through promoting gene expression of IGF-1 and IGF1R in chondrocytes: promoting anti-osteoarthritic activity.. PLoS One 2014;9(9):e107024.
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