Dexamethasone Facilitates NF-κB Signal Pathway in TNF-α Stimulated Rotator Cuff Tenocytes

Corticosteroids are commonly used for pain control in rotator cuff tear. Deregulated $NF-{\kappa}B$ activation is a hallmark of chronic inflammatory diseases and has been responsible for the pathogenesis of rotator cuff tear. The Dexamethasone(DEXA) is a synthetic corticosteroid. The purpose of this study was to examine the exact effect of dexamethasone on $NF-{\kappa}B$ signaling in rotator cuff tear. We measured $NF-{\kappa}B$ expression in four groups: control, $TNF-{\alpha}$-treated, DEXA-treated, and combined treatment with $TNF-{\alpha}$ and DEXA. Tenocytes were isolated from patients with rotator cuff tears and pre-incubated with $TNF-{\alpha}$ (10 ng/ml), DEXA ($1{\mu}M$), or both of them for 10 min, 1 h, and 2 h. Expression of p65, p50, and p52 in the nuclei and cytosol was analyzed by western blotting and immunofluorescence imaging using confocal microscopy. We also evaluated nucleus/cytosol (N/C) ratios of p65, p50, and p52. In our study, the combined treatment with DEXA and $TNF-{\alpha}$ showed increased N/C ratios of p65, p50, and p52 compared with those in the $TNF-{\alpha}$ group at all time points. Additionally, in the DEXA group, N/C ratios of p65, p50, and p52 gradually increased from 10 min to 2 h. In conclusion, DEXA promoted the nuclear localization of p65, p50, and p52, but was not effective in inhibiting the inflammatory response of $TNF-{\alpha}$-stimulated rotator cuff tear.