Leptin protects rat articular chondrocytes from cytotoxicity induced by TNF-α in the presence of cyclohexamide

Objective: Although leptin appears to be an important local and systemic factor influencing cartilage homeostasis, the role of leptin in chondrocyte death is largely unknown. Tumor necrosis factor alpha (TNF-alpha) is a pro-inflammatory cytokine that plays a central role in the pathogenesis of articular diseases. This study examines whether leptin modulates TNF-alpha-induced articular chondrocyte death. Methods: Primary rat articular chondrocytes were isolated from knee joint cartilage slices. To induce cell death, the chondrocytes were treated with TNF-alpha. To examine whether leptin modulates the extent of TNF-alpha-mediated chondrocyte death, the cells were pretreated with leptin for 3 h before TNF-alpha treatment followed by viability analysis. To examine the mechanism by which leptin modulates the extent of TNF-alpha-mediated chondrocyte death, we utilized mitochondrial membrane potential (MMP) measurements, flow cytometry, nuclear morphology observation, co-immunoprecipitation, western blot analysis and confocal microscopy. Results: We demonstrated that leptin suppresses TNF-a induced chondrocyte death. We further found that apoptosis partially contributes to TNF-alpha induced chondrocyte death while necroptosis primarily contributes to TNF-alpha induced chondrocyte death. In addition, we observed that leptin exerts anti-TNF-alpha toxicity via c-jun N-terminal kinase (JNK) in rat articular chondrocytes. Conclusion: Based on our findings, we suggest that the leptin present in the articular joint fluid protects articular chondrocytes against cumulative mechanical load and detrimental stresses throughout a lifetime, delaying the onset of degenerative changes in chondrocytes. We can further hypothesize that leptin protects articular chondrocytes against destructive stimuli even in the joints of osteoarthritis (OA) patients. (C) 2015 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.