Differences in tumor necrosis factor (TNF)alpha and TNF receptor-1-mediated intracellular signaling factors in normal, inflamed and scar-formed horse tendons.
Tumor necrosis factor (TNF) receptors (TNF-R)-mediated cell survival or apoptosis has been demonstrated in many cells, but little is known about survival or apoptotic signals via TNF-R1 in tendinocytes. In this study, we focused on four signaling factors, TNFalpha, TNF-R1, TNFR-associated factor2 (TRAF2) and caspase-3, in order to elucidate the signaling events in tendinocytes. Samples were obtained from normal, inflamed and scar-formed equine superficial digital flexor tendons. To detect these signaling factors, samples were subjected to immunohistochemistry and Western blot analysis, and some samples were also subjected to reverse transcription-polymerase chain reaction (RT-PCR), PCR-Southern blot analysis and in situ hybridization to detect the expression of TNFalpha mRNA. Distribution of the four factors differed depending on the tendon condition, normal, inflamed or scar-formed. In the normal tendon, large amounts of TRAF2 were found in tendinocytes, but the amounts of TNF-R1 were small. TNFalpha mRNA was expressed most highly in the inflamed tendon. TNF-R1, which was only faintly detected in the normal tendon, was detected at a high level in the inflamed tendon, and the amounts of TRAF2 and caspase-3 also increased. Activated caspase-3 was only detected in the inflamed tendon. TNFalpha mRNA was also expressed in the scar-formed tendon, though it showed weak signals, and the expression levels of TNF-R1, TRAF2 and caspase-3 proteins were very low. Two distinct intracellular signaling pathways of TNFalpha, which lead to cell survival and apoptosis, might be present in tendinocytes mediated through TNF-R1. These results, which reflect the dynamism of TNFalpha, provide important clues for means to prevent tendinopathy.
Hosaka
Yoshinao
Y
Department of Veterinary Anatomy, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Japan.
Kirisawa
Rikio
R
Ueda
Hiromi
H
Yamaguchi
Mamoru
M
Takehana
Kazushige
K
D000818:Animals; D015139:Blotting, Southern / Q000662:veterinary; D015153:Blotting, Western / Q000662:veterinary; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D017931:DNA Primers; D006734:Horse Diseases / Q000378:metabolism* / Q000473:pathology; D006736:Horses; D007150:Immunohistochemistry / Q000662:veterinary; D017403:In Situ Hybridization / Q000662:veterinary; D007249:Inflammation / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D015398:Signal Transduction / Q000502:physiology*; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism; D013710:Tendons / Q000378:metabolism* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D017931:DNA Primers; D047888:Receptors, Tumor Necrosis Factor, Type I; D047992:TNF Receptor-Associated Factor 2; D014409:Tumor Necrosis Factor-alpha; D053148:Caspase 3; D020169:Caspases