Prothymosin α lacking the nuclear localization signal as an effective gene therapeutic strategy in collagen-induced arthritis

Prothymosin alpha (ProT) is regulated by c-Myc, an oncoprotein overexpressed in synovium of rheumatoid arthritis, and is associated with cell proliferation. However, ProT also exerts immunomodulatory activities. The growth-promoting activity of ProT can be abolished by deleting its nuclear localization signal (NLS). In this study, we showed that AdProT Delta NLS, an adenoviral vector encoding ProT lacking the NLS, did not enhance the proliferation of synovial fibroblasts. AdProT Delta NLS treatment abolished the up-regulation of the MIP-1 alpha promoter activity induced by TNF-alpha in synovial fibroblasts. AdProT Delta NLS suppressed macrophage chemotaxis and reduced macrophage infiltration into the ankle joints in rats with collagen-induced arthritis (CIA). Neutralization test confirmed the involvement of MIP-1 alpha in macrophage chemotaxis. Administration of AdProT Delta NLS reduced the severity of CIA in the clinical, radiographic, and histological aspects. The levels of TNF-a (mean +/- SEM, 1261.9 +/- 107.9 vs 2880.1 +/- 561.4 pg/mg total protein; p < 0.05), IL-1 beta (56.8 +/- 8.0 vs 109.2 +/- 4.9 pg/mg total protein; p < 0.01), and MIP-1a (41.7 +/- 3.6 vs 55.2 +/- 1.1 pg/mg total protein; p < 0.05) in the ankle joints were lower in the AdProT Delta NLS-treated rats with CIA than those in their control counterparts. In the AdProT Delta NLS-treated ankle joints, matrix metalloproteinase-9 expression was decreased by 40% and infiltrating macrophages reduced by 50%. Our results demonstrate that intra-articular delivery of AdProT Delta NLS significantly ameliorated the clinical course of CIA in rats. This study is the first to suggest that ProT lacking the NLS may have therapeutic potential for the management of rheumatoid arthritis.