Interleukin-1beta and interleukin-6 disturb the antioxidant enzyme system in bovine chondrocytes: a possible explanation for oxidative stress generation.
OBJECTIVE
Beside matrix metalloproteinases, reactive oxygen species (ROS) are the main biochemical factors of cartilage degradation. To prevent ROS toxicity, chondrocytes possess a well-coordinated enzymatic antioxidant system formed principally by superoxide dismutases (SODs), catalase (CAT) and glutathione peroxidase (GPX). This work was designed to assess the effects of interleukin (IL)-1beta and IL-6 on the enzymatic activity and gene expression of SODs, CAT and GPX in bovine chondrocytes.


METHODS
Bovine chondrocytes were cultured in monolayer for 4-96 h in the absence or in the presence of IL-1beta (0.018-1.8ng/ml) or IL-6 (10-100 ng/ml). To study signal transduction pathway, inhibitors of mitogen-activated protein kinases (MAPK) (PD98059, SB203580 and SP600125) (5-20 microM) and nuclear factor (NF)-kappaB inhibitors [BAY11-7082 (1-10 microM) and MG132 (0.1-10 microM)] were used. SODs, CAT and GPX enzymatic activities were evaluated in cellular extract by using colorimetric enzymatic assays. Mn SODs, Cu/Zn SOD, extracellular SOD (EC SOD), CAT and GPX gene expressions were quantified by real-time and quantitative polymerase chain reaction (PCR).


RESULTS
Mn SOD and GPX activities were dose and time-dependently increased by IL-1beta. In parallel, IL-1beta markedly enhanced Mn SOD and GPX gene expressions, but decreased Cu/Zn SOD, EC SOD and CAT gene expressions. Induction of SOD enzymatic activity and Mn SOD mRNA expression were inhibited by NF-kappaB inhibitors but not by MAPK inhibitors. IL-6 effects were similar but weaker than those of IL-1beta.


CONCLUSIONS
In conclusion, IL-1beta, and to a lesser extend IL-6, dysregulates enzymatic antioxidant defenses in chondrocyte. These changes could lead to a transient accumulation of H(2)O(2) in mitochondria, and consequently to mitochondria damage. These changes contribute to explain the mitochondrial dysfunction observed in osteoarthritis chondrocytes.
Mathy-Hartert
M
M
Bone and Cartilage Research Unit, Department of Physical Medicine, University of Liège, CHU Sart-Tilman, 4000 Liège, Belgium.
Hogge
L
L
Sanchez
C
C
Deby-Dupont
G
G
Crielaard
J M
JM
Henrotin
Y
Y
D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002358:Cartilage, Articular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D002374:Catalase / Q000096:biosynthesis / Q000235:genetics; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005979:Glutathione Peroxidase / Q000096:biosynthesis / Q000235:genetics; D053583:Interleukin-1beta / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013482:Superoxide Dismutase / Q000096:biosynthesis / Q000235:genetics
D000975:Antioxidants; D004791:Enzyme Inhibitors; D053583:Interleukin-1beta; D015850:Interleukin-6; D016328:NF-kappa B; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D020928:Mitogen-Activated Protein Kinases