Measurement of radiographic changes in adjuvant-induced arthritis in rats by quantitative image analysis.

OBJECTIVE: To apply quantitative analytical methods to the evaluation of radiographic images in experimental arthritis. METHODS: Adjuvant was used to induce arthritis in rats. Arthritis progression was followed by conventional methods. In addition, digitized images of radiographs of the calcaneus were examined for changes in the mean and in the distribution pattern of gray values. Periosteal new bone formation was measured as an increase in image area of the calcaneus. RESULTS: Significant changes in the gray value profile and increases in periosteal bone formation occurred in arthritic rats. More extensive changes occurred in Lewis rats than in Sprague-Dawley rats. Analysis of serial radiographs revealed an initial decrease in the density of juxtaarticular bone, followed by progressive increases in gray value variation due to concurrent bone loss and bone formation. Eventually, bone formation in arthritic rats resulted in increased gray values above those in nonarthritic rats. CONCLUSION: Image analysis represents a sensitive, quantitative method for detecting radiographic changes in experimental arthritis.

Cysteine proteinase inhibitors decrease articular cartilage and bone destruction in chronic inflammatory arthritis.

OBJECTIVE: To determine the effects of peptidyl fluoromethyl ketones on the in vitro activity of purified cathepsins B and L, on tissue cysteine proteinase activity, and on cartilage and bone destruction in experimental arthritis. METHODS: The effects of the fluoroketones on cathepsins B and L in vitro and the effects of oral administration of fluoroketones on ex vivo cysteine proteinase activity in tissue homogenates were determined by measuring the inhibition of fluorogenic substrate cleavage. To determine the effects on arthritis, animals were injected with adjuvant or type II collagen, treated orally with the fluoroketones, and the severity of arthritis was assessed by clinical, histologic, and radiologic methods. RESULTS: All of the fluoroketones tested were potent inhibitors of purified cathepsins B and L activity. Oral administration of the fluoroketones reduced tissue cysteine proteinase activity by up to 77%. In addition, fluoroketone treatment significantly reduced the severity of clinical joint disease and decreased the destruction of articular cartilage and bone. Quantitative analysis of radiographic images indicated that treatment significantly reduced soft tissue changes, periosteal proliferation, and bone erosion, but only partially reduced juxtaarticular osteoporosis. CONCLUSION: These studies suggest that cysteine proteinase inhibitors may limit tissue destruction in diseases such as rheumatoid arthritis.

The effects of fluoromethyl ketone inhibitors of cathepsin B on adjuvant induced arthritis.

Peptidyl fluoromethyl ketones with the structure carbobenzoxy (Z)-L-phenylalanine-L-alanine-CH2F (MDL 201,053), and its diastereomer Z-L-phenylalanine-D-alanine-CH2F (MDL 201,117), were synthesized and evaluated in vitro for inhibition of purified human cathepsin B. MDL 201,053 was shown to be a potent inhibitor of cathepsin B activity, whereas MDL 201,117 was more than 100-fold less active. In rats with adjuvant induced arthritis, oral administration of MDL 201,053 (13 or 34 mg/kg/day), but not MDL, 201,117 (28 mg/kg/day), significantly decreased the severity of gross clinical arthritis and reduced histologically graded articular cartilage and bone destruction by 76 to 100%. Quantitative image analysis of radiographs indicated that MDL 201,053 treatment significantly reduced bone density changes and inhibited focal bone erosion that normally occur during the course of adjuvant disease. MDL 201,117 had no significant effect on cartilage or bone destruction by any of the evaluation methods used. The effects of MDL 201,053 treatment were dose dependent and treatment was at least partially effective when initiated after the onset of disease. Our studies suggest that inhibitors of cathepsin B may be useful for the treatment of chronic inflammatory joint disease.