Tendon overuse injuries and tendinitis are accompanied by catabolic processes 
and apoptosis of tenocytes. However, the precise molecular mechanisms of the 
destructive processes in tendon are not fully understood. Sirt-1, a nicotinamide 
adenine dinucleotide (NAD(+))-dependent deacetylase, has been linked to 
transcriptional silencing and appears to play a key role in inflammation. The 
purpose of this study was to examine whether down-regulation of Sirt-1 using 
antisense oligonucleotides (ASO) affects inflammatory and apoptotic signaling in 
tenocytes. Transient transfection of tenocytes with ASO against Sirt-1 induced 
expression of Bax and other proteins involved in apoptosis (cleaved caspase-3 
and poly(ADP-ribose)polymerase), acetylation of tumor suppressor p53, and 
mitochondrial degradation. Interestingly, Sirt-1 was found to interact directly 
with p53. In contrast, Sirt-1 activator resveratrol inhibited interleukin-1β 
(IL-1β)- and nicotinamide-induced NF-κB activation and p65 acetylation and 
suppressed the activation of IκB-α kinase. Resveratrol also reversed the IL-1β- 
or nicotinamide-induced up-regulation of various gene products that mediate 
inflammation (cyclooxygenase-2) and matrix degradation (matrix 
metalloproteinase-9) that are known to be regulated by NF-κB. Knockdown of 
Sirt-1 by using ASO abolished the inhibitory effects of resveratrol on 
inflammatory and apoptotic signaling including Akt activation and SCAX 
suppression. Down-regulation of histone deacetylase Sirt-1 by mRNA interference 
abrogated the effect of resveratrol on NF-κB suppression, thus highlighting the 
crucial homeostatic role of this enzyme. Overall, these results suggest for the 
first time that Sirt-1 can regulate p53 and NF-κB signaling via deacetylation, 
demonstrating a novel role for resveratrol in the treatment of 
tendinitis/tendinopathy.