ABSTRACT
<p><b>OBJECTIVE</b>To observe the effects of intra-articular ozone injection at different concentrations on the contents of tumor necrosis factor-α (TNF-α), TNF receptor I (TNFR I), and TNFR II in the serum and synovium of rats with rheumatoid arthritis (RA) and explore the therapeutic mechanism of ozone in RA treatment.</p><p><b>METHODS</b>Forty-eight Wistar rats were randomized into 8 groups, including 5 ozone groups receiving intra-articular injection of 10, 20, 30, 40 or 50 µg/ml ozone, a blank control group, an oxygen group and a RA model group. All the rats, except for those in the blank control group, were subjected to hypodermic injection of bovine collagen II and complete Freunds adjuvant to induce RA. Ozone treatment was administered once weekly for 3 weeks starting at 21 days after the modeling. The swelling and thickness of the hind paws were observed, and the serum and synovial contents of TNF-α, TNFR I, and TNFR II were detected.</p><p><b>RESULTS</b>At the end of treatment, the paw thickness was reduced significantly in rats with 40 µg/ml ozone injection compared with that in the model RA group (P<0.01). The serum contents of TNF-α, TNFR I and TNFR II showed no significant difference between the RA model group, oxygen group and the ozone groups, but their synovial contents showed significant reductions in rats with 40 and 50 µg/ml ozone injection (P<0.01); the synovial TNFR I was significantly higher in 40 µg/ml ozone group than in the model group (P<0.05).</p><p><b>CONCLUSION</b>Intra-articular injection of 40 µg/ml ozone can attenuate synovitis in rats with RA, the mechanism of which may involve the inhibition of TNF-α and TNFR II activity and enhancement of TNFR I activity in the synovium.</p>