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SUMMARY

In each of 4 horses, sterile synovitis was induced by intra-articular injection of 3 μg of Escherichia coli endotoxin (lipopolysaccharide, LPS) into one antebrachiocarpal joint; an equal volume (2 ml) of phosphate-buffered saline solution (PBSS) was injected into the opposite, control carpus. Blood and 1.5 ml of synovial fluid were obtained at postinjection hours (pih) 0, 2, 4, 8, 12, 18, 42, 66, and 144. Synovial fluid sample collection was accomplished by use of an indwelling, intra-articular catheter through pih 12, and by arthrocentesis subsequently. Joint fluid samples were analyzed for cell counts, protein concentration, cytologic variables, and tumor necrosis factor (tnf), interleukin 6 (IL-6), and prostaglandin E2 (PGE2) values. Tumor necrosis factor and 1L-6 activities and WBC count were also measured in blood. To monitor local inflammation, skin temperature of each carpus was imaged, using a thermographic scanner prior to each sample collection time.

Horses had minimal systemic effects. Mean (± SEM) rectal temperature increased significantly to 39 02 ± 0.15 C only at pih 18 after intra-articular injection of LPS. One horse had signs of mild depression from pih 7 to 18, but its vital signs did not change appreciably. Each horse had mild signs of discomfort in the LPS-injected limb from pih 1 to 3 until pih 8 to 10. Mean peak surface temperature of the LPS-injected carpi was significantly higher than that of control carpi from pih 8 to 144 (P < 0.05).

Mean synovial fluid WBC count in the LPS-injected and control carpi increased after injection and peaked by pih 8 (193,125 ± 8,528 cells/μl, LPS-treated; 16,425 ± 8,336 cells/μl, controls). Mean values for LPS-treated (principal) joints were significantly greater than values for control joints from pih 2 until after pih 66 (P < 0.05). Mean synovial fluid protein concentration increased in the principal and control joints, with values for the principal joints remaining significantly greater than values for control joints from pih 4 to 144 (P < 0.05). Mean TNF activity in synovial fluid was maximal at pih 2 (10,573 ± 5,924 U/ml). Interleukin-6 activity increased more gradually and peaked at pih 8 (1.78 ± 0.71 × 106 U/ml). Tumor necrosis factor activity did not increase above the minimal detectable value of 6 U/ml in the control joints. Mean PGE2 concentration in the principal joints peaked by pih 2 (3.6 ± 0.37 ng/ml) and remained significantly (P < 0.05) greater than the value for control joints from pih 2 through 66. These results indicate that a humane model of synovitis was created by intra-articular injection of LPS and can be used to establish the basic responses of synovial TNF, IL-6, and PGE2 in horses with early inflammatory joint disease.

Free access
in American Journal of Veterinary Research

SUMMARY

Six horses received intra-articular injections of a mixture of 1 μg of endotoxin/5 mg of equine tumor necrosis factor (eqTNF) monoclonal antibody in 1 antebrachiocarpal joint and an equal volume (2 ml) of 1 μg of endotoxin/5 mg of control antibody in the opposite joint. Synovial fluid sample collection (1 ml) was accomplished by use of an indwelling, intra-articular catheter at postinjection hours (pih) 0, 1, 1.5, 2, 5, and 8, and by arthrocentesis at pih 24. Joint fluid samples were analyzed for nucleated cell count, protein concentration, and tnf, interleukin 6 (il-6), il-1, and il-1-inhibitory activities. To monitor local inflammation, each carpus was graded semiquantitatively for swelling prior to each sample collection.

Tumor necrosis factor, il-1, or il-1-inhibitory activity was not detected in any synovial fluid sample collected before endotoxin/antibody was administered. However, low il-6 activity (< 100 U/ml) was found in 2 of 12 preinjection samples. In joints injected with endotoxin/control antibody mixture, maximal mean ± sem activities for tnf (1,019 ± 310 U/ml), il-1 (173 ± 102 U/ml), and il-6 (10.8 ± 3.1 × 104 U/ml) were observed at pih 2, 5, and 8, respectively. Tumor necrosis factor and il-1 activities returned to baseline values by pih 8 and 24, respectively; however, il-6 activity remained high. Interleukin 1-inhibitory activity (27.4 ± 2.25 IU/ml) was detected in all pih-24 samples from control joints, but was not detected at any other time in control joints (limit of detection, 20 IU/ml).

Tumor necrosis factor activity was not detected in any synovial fluid sample from joints treated with endotoxin/eqTNF antibody. In contrast, endotoxin-induced mean synovial il-1 and il-6 activities were not reduced significantly by eqTNF antibody. Mean il-1-inhibitory activity (pih 24) was higher in eqTNF antibody-treated joints (41.0 ± 7.7 IU/ml) than in control joints, but the difference was not significant. Mean wbc count and protein concentration in control and treated joints were maximal at pih 8. The curves for mean values of wbc count and total protein concentration were not significantly different in treated versus control joints. Swelling in each treated joint was either less than or the same as that in the opposite control joint at every time in the initial 8 pih. There was significant (P = 0.043) difference between treated and control joints at pih 5 and 8. These results describe a profile of synovial fluid tnf, il-1, il-6 bioactivities, and il-1-inhibitory activity during the initial 24 hours of synovitis induced by intra-articular administration of endotoxin in horses. Our eqTNF monoclonal antibody was effective in neutralizing tnf activity in synovial fluid when administered intra-articularly with endotoxin in horses. The induction of il-1, il-1-inhibitory activity, il-6, wbc, and total protein concentration responses are largely independent of tnf activity in synovial fluid of horses receiving endotoxin intra-articularly.

Free access
in American Journal of Veterinary Research

were trained by means of positive reinforcement techniques to accept handling and all experimental procedures, including radiocarpal arthrocentesis. Induction of synovitis —Synovitis was induced by means of aseptic IA injection (21-gauge needle) of 3

Full access
in American Journal of Veterinary Research