Effects of interleukin-1 on calcium signaling and the increase of filamentous actin in isolated and in situ articular chondrocytes.


Journal Article

OBJECTIVE: To determine whether interleukin-1 (IL-1) initiates transient changes in the intracellular concentration of [Ca2+]i and the organization of filamentous actin (F-actin) in articular chondrocytes. METHODS: Articular chondrocytes within cartilage explants and enzymatically isolated chondrocytes were loaded with Ca(2+)-sensitive fluorescence indicators, and [Ca2+]i was measured using confocal fluorescence ratio imaging during exposure to 10 ng/ml IL-1alpha. Inhibitors of Ca2+ mobilization (Ca(2+)-free medium, thapsigargin [inhibitor of Ca-ATPases], U73122 [inhibitor of phospholipase C], and pertussis toxin [inhibitor of G proteins]) were used to determine the mechanisms of increased [Ca2+]i. Cellular F-actin was quantified using fluorescently labeled phalloidin. Toxin B was used to determine the role of the Rho family of small GTPases in F-actin reorganization. RESULTS: In isolated cells on glass and in in situ chondrocytes within explants, exposure to IL-1 induced a transient peak in [Ca2+]i that was generally followed by a series of decaying oscillations. Thapsigargin, U73122, and pertussis toxin inhibited the percentage of cells responding to IL-1. IL-1 increased F-actin content in chondrocytes in a manner that was inhibited by toxin B. CONCLUSION: Both isolated and in situ chondrocytes respond to IL-1 with transient increases in [Ca2+]i via intracellular Ca2+ release mediated by the phospholipase C and inositol trisphosphate pathways. The influx of Ca2+ from the extracellular space and the activation of G protein-coupled receptors also appear to contribute to these mechanisms. These findings suggest that Ca2+ mobilization may be one of the first signaling events in the response of chondrocytes to IL-1.

Full Text

Cited Authors

  • Pritchard, S; Guilak, F

Published Date

  • July 2006

Published In

Volume / Issue

  • 54 / 7

Start / End Page

  • 2164 - 2174

PubMed ID

  • 16802354

Pubmed Central ID

  • 16802354

Electronic International Standard Serial Number (EISSN)

  • 1529-0131

International Standard Serial Number (ISSN)

  • 0004-3591

Digital Object Identifier (DOI)

  • 10.1002/art.21941


  • eng