Small hyaluronan oligosaccharides induce inflammation by engaging both toll-like-4 and CD44 receptors in human chondrocytes.
Small degradation fragments of hyaluronan (HA) may stimulate an inflammatory response in a variety of tissues at the injury site. HA oligosaccharides are endogenous ligands for the cluster determinant 44 (CD44) receptor as well as for toll-like receptor 4 (TLR-4). Previous data have shown that HA fragments may induce pro-inflammatory cytokine expression by interacting with both the CD44 receptor and TLR-4. CD44 and TLR-4 stimulation activates different inflammatory pathways that culminate with the activation of the transcriptional nuclear factor kappaB (NF-kappaB) which is responsible for the expression of inflammation mediators such as tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-1 beta (IL-1beta). The aim of this study was to investigate the inflammatory effects of very small HA oligosaccharides on both TLR-4 and CD44 involvement in normal human articular chondrocytes. Adding HA fragments to chondrocyte cultures up-regulated CD44 and TLR-4 expression, activated NF-kappaB translocation and increased the pro-inflammatory cytokines TNF-alpha, IL-6 and IL-1beta. The addition of a specific CD44 blocking antibody reduced CD44 and all inflammatory cytokine expression as well as protein production. However, cytokine expression remained significantly higher than in untreated chondrocytes. TLR-4 expression was not affected. The treatment with TLR-4 blocking antibody decreased TLR-4 and inflammatory cytokine expression, although cytokine expression was significantly higher than in control cells. CD44 expression was unaffected. The addition of both CD44 and TLR-4 blocking antibodies significantly reduced CD44, TLR-4 and inflammatory cytokine expression.
Campo
Giuseppe M
GM
Department of Biochemical, Physiological and Nutritional Sciences, University of Messina, Italy. gcampo@unime.it
Avenoso
Angela
A
Campo
Salvatore
S
D'Ascola
Angela
A
Nastasi
Giancarlo
G
Calatroni
Alberto
A
D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000473:pathology; D006801:Humans; D018960:Hyaluronan Receptors / Q000502:physiology*; D006820:Hyaluronic Acid / Q000633:toxicity*; D007249:Inflammation / Q000139:chemically induced*; D009844:Oligosaccharides / Q000633:toxicity*; D051197:Toll-Like Receptor 4 / Q000502:physiology*
C497483:CD44 protein, human; D018960:Hyaluronan Receptors; D009844:Oligosaccharides; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D006820:Hyaluronic Acid