An adenosine A2A receptor agonist reduces interleukin-8 expression and glycosaminoglycan loss following septic arthrosis

The purpose of this study was to determine whether an adenosine A(2A) receptor agonist (ATL146e) might augment the current treatment regimen of antibiotics plus irrigation and debridement to prevent the arthritic effects associated with joint sepsis. Staphylococcus aureus bacteria were injected into knees of rabbits, which were divided into 4 treatment groups (12 rabbits per group): no treatment, ATL146e, only, antibiotics only, or antibiotics plus ATL146e. Analysis at days 1, 3, and 7 consisted of gross joint appearance, synovial fluid, serum, histologic, immunohistochemical, and biochemical analysis. Synovial fluid cultures at day 7 were negative in all antibiotic and antibiotic plus ATL146e treated knees indicating clearance of bacteria. Average WBC counts from synovial fluid aspirates significantly decreased with treatment of antibiotics alone and antibiotics plus ATL146e. Treatment with antibiotics plus ATL146e significantly decreased the Interleukin-8 content when compared to other treatment groups (p < 0.001) indicating inflammatory response suppression. Histologic grading resulted in notably improved scores in the antibiotics plus ATL146e group compared to other treatment groups (p <= 0.001). Glycosaminoglycan assay values were significantly greater in the ATL146e plus antibiotics group compared to the untreated control group (p < 0.04) indicating chondroprotection. The results of this study indicate that administration of an adenosine A2A agonist in combination with antibiotic therapy diminishes joint WBC chemotaxis and reduces joint inflammation, while not compromising the clearance of intraarticular bacteria in a rabbit model. Early bacterial clearance with modulation of the inflammatory response appears to prevent the early degradative effects of joint sepsis. (c) 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.