Palmitate has proapoptotic and proinflammatory effects on articular cartilage and synergizes with interleukin-1

Abstract

Objectives Obesity is a major risk factor for the development of osteoarthritis (OA) that is associated with a state of low-grade inflammation, and increased circulating adipokines and free fatty acids (FFA). The aim of this study was to analyze effects of saturated (palmitate) and monounsaturated (oleate) free fatty acids (FFA) on articular chondrocytes, synoviocytes and cartilage. Methods Human articular chondrocytes and fibroblast-like synoviocytes obtained from young healthy donors, and OA chondrocytes from patients undergoing totalknee replacement were treated with palmitate or oleate alone or with interleukin 1-β (IL-1β). Cell viability, caspase activation, and gene expression of proinflammatory factors, extracellular matrix proteins, and proteases were studied. In addition, chondrocyte viability, interleukin-6 (IL-6) production and matrix damage were assessed in bovine and human articular cartilage explants cultured with FFA with or without IL-1β. Results Palmitate, but not oleate, induced caspase activation and cell death in IL-1β-stimulated normal chondrocytes, and upregulated il6 and cox2 expression in chondrocytes and fibroblast-like synoviocytes through toll-like receptor-4 signaling. In cartilage explants, palmitate induced chondrocyte death, IL-6 release and extracellular matrix degradation. Palmitate synergized with IL-1β in stimulating proapoptotic and proinflammatory cellular responses. Pharmacological inhibition of caspases or TLR-4 signaling reduced palmitate and IL-1β-induced cartilage damage. Conclusions Palmitate acts as a pro-inflammatory and catabolic factor that, in synergy with IL-1β, induces chondrocyte apoptosis and articular cartilage breakdown. Collectively, our data suggest that elevated levels of saturated FFA often found in obesity may contribute to OA pathogenesis. © 2014 American College of Rheumatology.

Copyright © 2014 American College of Rheumatology.

KEYWORDS:

Osteoarthritis, cartilage, fatty acids