Components generated locally as well as serum alter the phlogistic effect of monosodium urate crystals in vivo

Proteins binding monosodium urate (MSU) crystals alter their phlogistic potential in vitro and in vivo. These proteins and other materials capable of interacting with crystals could enter the joint space from the circulation and/or could be produced locally. Using the rat subcutaneous air pouch synovium-like model, we observed different effects of collected pouch fluid supernatants from acute (6 h) and from subsiding (72 h) inflammation, and from autologous rat serum on MSU crystal induced inflammation in new air pouches. Plain crystals at 6 h produced a mean leukocyte count (WBC) of 18,156/mm3 with 12% of cells showing phagocytosis of MSU; reaction to plain crystals at 72 h had subsided to only 75 WBC/mm3 and 1% phagocytosis; new crystals preincubated in supernatant from acutely inflamed 6 h air pouches produced higher numbers of WBC in new pouches at 6 h (34,044/mm3); while crystals preincubated in 72 h supernatant gave only 9,825/mm3 and 7% phagocytosis; crystals preincubated in rat serum produced similar pouch WBC to plain crystals at 6 h, but resulted in only 2% phagocytosis. Our study provides evidence that components generated locally during subsiding inflammation as well as serum components could bind to MSU crystals and affect the generation of chemotactic factors and/or crystal phagocytosis contributing in the self-limited nature of acute gouty arthritis.