Purpose: The aim of this study was to determine the effect of hyaluronic acid (HA) on cyclooxygenase (COX)-2 expression in orbital fibroblasts from patients with thyroidassociated ophthalmopathy (TAO).
Methods: Primary cultured orbital fibroblasts were obtained from patients with TAO and non- TAO subjects. Dermal and conjunctival fibroblasts were cultured from the eyelid skin of subjects undergoing cosmetic lid surgery or cataract surgery, respectively. The cells were treated with HA and the transcriptional and translational levels of COX-2 were measured. The expression of CD44 on each type of cells was determined, and the involvement of CD44 in the HA-induced COX-2 increase in orbital fibroblasts from patients with TAO was evaluated by using CD44 knockdown cells and by pretreatment with neutralizing antibody. The relevance of the mitogen-activated protein kinase (MAPK) or nuclear factor kappa-light-chain-enhancer of activated B cells (NF-jB)-mediated signaling pathway was assessed by immunoblotting for the phosphorylated form of each MAPK or IκB and by using specific inhibitors to these pathways.
Results: Hyaluronic acid increased COX-2 expression in orbital fibroblasts from patients with TAO, which was not observed in the cells from non-TAO subjects and conjunctival or dermal fibroblasts. Orbital fibroblasts from patients with TAO expressed significantly higher level of CD44 than non-TAO cells, and the increased COX-2 expression by HA in these cells was attenuated by knockdown or neutralizing of CD44. Hyaluronic acid induced MAPK and IκB phosphorylation; and cotreatment with specific MAPK or NF-κB inhibitors halted HA-induced transcription of COX-2, suggesting the involvement of these signaling pathways.
Conclusions: Hyaluronic acid induced COX-2 expression in orbital fibroblasts from patients with TAO via CD44 through the MAPK and NF-κB-mediated signaling pathways. These results suggest that HA may have a proinflammatory role in the pathogenesis of TAO by inducing COX-2.
- Hyaluronic acid
- Orbital fibroblast
- Thyroid-associated ophthalmopathy