POSTER NO: 413

Suppression of inflammation and gelatinase activity by gene transfer of extracellular superoxide dismutase (EC-SOD) and catalase in experimental arthritis

¹L. Dai, ¹A. Claxson, ²S. Marklund, ¹Y. Chernajovsky, ¹P.G. Winyard
¹Bone and Joint Research Unit, Barts and The London School of Medicine and Dentistry, Charterhouse Square, London, EC1M 6BQ, U.K., ²Department of Clinical Chemistry, Umeå University Hospital, Umeå, Sweden.

Background: Reactive oxygen species (ROS) have been implicated in the pathogenesis of rheumatoid arthritis. ROS are able to activate transcription factors, such as NF-? B and AP-1, which are involved in the regulation of the production of inflammatory mediators. A wide range of pro-inflammatory cytokines, such as TNF-alpha and IL-1, and a number of matrix metalloproteinases, including gelatinases A and B, have been implicated in the pathogenesis of rheumatoid arthritis. Overexpression of the antioxidant enzymes, EC-SOD and catalase, may block radical-induced events, reducing the inflammatory response and tissue destruction in joints. Methods: Immortalised rat synoviocytes were permanently transfected with a human EC-SOD expression plasmid (pEC-SODZeo) or a human catalase expression plasmid (pCatalaseZeo) to create cells overexpressing EC-SOD or catalase. The cells were engrafted in knee joints of rats at the time of the induction of monarticular antigen-induced arthritis (AIA). The effect of gene transfer of EC-SOD, catalase, and a combination of both on knee joint swelling and gelatinases A and B were assessed. In the control group AIA was induced, but the animals were engrafted with synoviocytes transfected with the plasmid without an insert. Results: An injection of EC-SOD- or catalase-overexpresing cells, or both, into rat knee joints produced a statistically significant suppression of knee joint swelling compared with animals in the control group. Gelatinase activity in synovial tissues was assayed by zymography. Latent gelatinase B, and latent and activated gelatinase A were seen in the samples from the animals in the control group. In contrast, animals treated with EC-SOD, or catalase, or the combination of both had lower levels of gelatinases A and B. The average gelatinase activities in the samples from these three groups were 52.6%, 42.6%, and 33.5% of the control group, respectively. There was a statistically significant difference between the control group and all three of the treated groups (P<0.05). Conclusion: The results from this study suggest that both the superoxide radical and hydrogen peroxide are involved in the development of AIA. Local expression of the antioxidant enzymes, EC-SOD and catalase effectively reduced the inflammation and gelatinase activity in this model.

This work is supported by the Arthritis Research Campaign (UK).