Although tumor necrosis factor (TNF) alpha is an important key factor in degeneration of equine superficial digital flexor tendon (SDFT), the dynamism of TNF receptors and associated factors on tendinocytes has not been elucidated. To reveal signaling events mediated by TNF-receptors (TNF-Rs) in tendinocytes, we focused on four signaling factors, TNF-R1, TNF-R2, TNF-Rassociated factor 2 (TRAF2) and nuclear factor-kappa B (NE-KappaB) , and investigated the distribution and production of these factors. Cultured tendinocytes were obtained from SDFTS of thoroughbred horses. The tendinocytes were treated with 10ng/ ml equine TNFAlpha medium for 6 hours and then the four factors on tendinocytes were visualized by using an immunohistochemical method, and the amounts of the four factors were determined by Western blot analysis. Although TNF-R1 and TNF-R2 co-localized on the same tendinocyte, in untreated control cells (normal condition), immunoreactivity against TNF-R1 was very weak but TNF-R2 showed a strong reaction. However, TNF-R1 showed the same high level of reaction as TNF-R2 in TNFAlpha-treated cells (inflamed condition). Intense TRAF2 and NF-KappaB were detected at inflamed condition, however both factors were also detected at normal condition. The distinct distributions of the four factors under different conditions (normal and inflamed condition) in uitro not only reflect the dynamism of the cytokines but may also provide important clues for a means to prevent from occurrence of tendonitis and progress of tendon degeneration.

The responses of plasma cortisol and adrenocorticotropic hormone (ACTH) were examined to intravenous injection of recombinant bovine tumor necrosis factor-alpha (TNF-alpha) and interferon-y (INF-gama) in Holstein cows. INF-gamain-duced dose-dependent rises in the plasma levels of both cortisol and ACTH, while TNF-alpha induced comparable plasma cortisol responses with much smaller rises in plasma ACTH. The results suggest a direct stimulatory action of TNF-alpha on cortisol secretion from the adrenal gland in cattle.