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

Prothymosin α (ProT) is regulated by c-Myc, an oncoprotein overespressed 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 AdProTΔNLS, an adenoviral vector encoding ProT lacking the NLS, did not enhance the proliferation of synovial fibroblasts. AdProTΔNLS treatment abolished the up-regulation of the MIP-1α promoter activity induced by TNF-α in synovial fibroblasts. AdProTΔNLS suppressed macrophage chemotasis and reduced macrophage infiltration into the ankle joints in rats with collagen-induced arthritis (CIA). Neutralization test confirmed the involvement of MIP-1α in macrophage chemotasis. Administration of AdProTΔNLS reduced the severity of CIA in the clinical, radiographic, and histological aspects. The levels of TNF-α (mean ± SEM, 1261.9 ± 107.9 vs 2880.1 ± 561.4 pg/mg total protein; p < 0.05), IL-1β (56.8 ± 8.0 vs 109.2 ± 4.9 pg/mg total protein; p < 0.01), and MIP-1α (41.7 ± 3.6 vs 55.2 ± 1.1 pg/mg total protein; p < 0.05) in the ankle joints were lower in the AdProTΔNLS-treated rats with CIA than those in their control counterparts. In the AdProTΔNLS-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 AdProTΔNLS 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.