Interleukin-1β and interleukin-6 disturb the antioxidant enzyme system in bovine chondrocytes: a possible explanation for oxidative stress generation 1

SummaryObjectiveBeside 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)-1β and IL-6 on the enzymatic activity and gene expression of SODs, CAT and GPX in bovine chondrocytes.MethodsBovine chondrocytes were cultured in monolayer for 4–96 h in the absence or in the presence of IL-1β (0.018–1.8 ng/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 μM) and nuclear factor (NF)-κB inhibitors [BAY11-7082 (1–10 μM) and MG132 (0.1–10 μM)] 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).ResultsMn SOD and GPX activities were dose and time-dependently increased by IL-1β. In parallel, IL-1β 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-κB inhibitors but not by MAPK inhibitors. IL-6 effects were similar but weaker than those of IL-1β.ConclusionsIn conclusion, IL-1β, and to a lesser extend IL-6, dysregulates enzymatic antioxidant defenses in chondrocyte. These changes could lead to a transient accumulation of H2O2 in mitochondria, and consequently to mitochondria damage. These changes contribute to explain the mitochondrial dysfunction observed in osteoarthritis chondrocytes.