Loss of p53-mediated suppression by its dominant-negative counterpart is commonly observed in human cancers, and activating p73 is a therapeutic strategy in p53-mutated oncological patients. In synovial fibroblasts (SFs) from rheumatoid arthritis (RA), mutant p53 can lead to the transformation-like features with resistance to the apoptosis induction. We examined whether intra-articular (i.a.) administration of p53-derived hybrid peptides to activate p73 can induce apoptosis of SFs by using adenoviral vectors encoding 37 amino acid (Ad37AA), a p53-derived hybrid peptide capable of activating p73, to transduce SFs in vitro and inject collagen-induced arthritis (CIA) joints in vivo. Increased p73 expression was found in synovial lining layers and SFs of RA patients and CIA rats. Higher expression of p53 up-regulated modulator of apoptosis (PUMA) and Bax with enhanced apoptosis were found in Ad37AA-transduced SFs, and silencing p73 abrogated the up-regulation of PUMA and Bax. Articular indexes and histologic scores were reduced in Ad37AA-injected joints with decreased SF densities, increased apoptotic cell numbers, and higher PUMA expression levels. We demonstrate that i.a. administration of p53-derived hybrid peptides can activate p73 to induce apoptosis of SFs and ameliorate the rheumatoid joint, implicating an enhancement of the p73-dependent apoptotic mechanism as a pharmacological strategy in the RA therapy.
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