Mitochondrial activity is modulated by TNFalpha and IL-1beta in normal human chondrocyte cells

Osteoarthritis Cartilage. 2006 Oct;14(10):1011-22. doi: 10.1016/j.joca.2006.03.008. Epub 2006 May 5.


Objective: Pro-inflammatory cytokines play an important role in osteoarthritis (OA). In osteoarthritic cartilage, chondrocytes exhibit an alteration in mitochondrial activity. This study analyzes the effect of tumor necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta) on the mitochondrial activity of normal human chondrocytes.

Materials and methods: Mitochondrial function was evaluated by analyzing the activities of respiratory chain enzyme complexes and citrate synthase, as well as by mitochondrial membrane potential (Deltapsim) and adenosine triphosphate (ATP) synthesis. Bcl-2 family mRNA expression and protein synthesis were analyzed by RNase protection assay (RPA) and Western-blot, respectively. Cell viability was analyzed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and apoptosis by 4', 6-diamidino-2-phenylindole dihydrochloride (DAPI) stain. Glycosaminoglycans were quantified in supernatant by a dimethyl-methylene blue binding assay.

Results: Compared to basal cells, stimulation with TNFalpha (10 ng/ml) and IL-1beta (5 ng/ml) for 48 h significantly decreased the activity of complex I (TNFalpha=35% and IL-1beta=35%) and the production of ATP (TNFalpha=18% and IL-1beta=19%). Both TNFalpha and IL-1beta caused a definitive time-dependent decrease in the red/green fluorescence ratio in chondrocytes, indicating depolarization of the mitochondria. Both cytokines induced mRNA expression and protein synthesis of the Bcl-2 family. Rotenone, an inhibitor of complex I, caused a significant reduction of the red/green ratio, but it did not reduce the viability of the chondrocytes. Rotenone also increased Bcl-2 mRNA expression and protein synthesis. Finally, rotenone as well as TNFalpha and IL-1beta, reduced the content of proteoglycans in the extracellular matrix of normal cartilage.

Conclusion: These results show that both TNFalpha and IL-1beta regulate mitochondrial function in human articular chondrocytes. Furthermore, the inhibition of complex I by both cytokines could play a key role in cartilage degradation induced by TNFalpha and IL-1beta. These data could be important for understanding of the OA pathogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Apoptosis
  • Cartilage, Articular / physiology*
  • Chondrocytes / drug effects*
  • Glycosaminoglycans / metabolism
  • Humans
  • Interleukin-1beta / pharmacology*
  • Middle Aged
  • Mitochondria / physiology*
  • Proteins / metabolism
  • Proteoglycans / metabolism
  • RNA, Messenger / metabolism
  • Rotenone / pharmacology
  • Tumor Necrosis Factor-alpha / pharmacology*
  • Uncoupling Agents / pharmacology


  • Glycosaminoglycans
  • Interleukin-1beta
  • Proteins
  • Proteoglycans
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha
  • Uncoupling Agents
  • Rotenone
  • Adenosine Triphosphate