INDUCTION OF A SELECTIVE AND PERSISTENT EXTRAVASATION OF NEUTROPHILS INTO THE PERITONEAL-CAVITY BY TRYPTASE MOUSE MAST-CELL PROTEASE-6

Recombinant mouse mast cell protease 6 (mMCP-6) nas generated to study the role of this tryptase in inflammatory reactions. Seven to forty-e ight hours after the i,p, injection of recombinant mMCP-6 into BALB/c, mast cell deficient WCB6F(1)-Sl/Sl(d) C5-deficient, or mMCP-5-null mi ce, the number of neutrophils in the peritoneal cavity of each animal increased significantly by >50-fold, The failure of the closely relate d recombinant tryptase mMCP-7 to induce a comparable peritonitis indic ates that the substrate specificities of the two tryptases are very di fferent, Unlike most forms of acute inflammation, the mMCP-6-mediated peritonitis was relatively long lasting and neutrophil specific. Mouse MCP-6 did not induce neutrophil chemotaxis directly in an in vitro as say, but did promote chemotaxis of the leukocyte in the presence of en dothelial cells. Mouse MCP-6 did not induce cultured human endothelial cells to express TNF-alpha, RANTES, IL-1 alpha, or IL-6, However, the tryptase induced endothelial cells to express large amounts of IL-8 c ontinually over a 40-h period. Neither enzymatically active mMCP-7 nor enzymatically inactive pro-mMCP-6 was able to induce endothelial cell s to increase their expression of IL-8, Although the mechanism by whic h mMCP-6 induces neutrophil accumulation in tissues remains to be dete rmined, the finding that mMCP-6 induces cultured human endothelial cel ls to selectively release large amounts of IL-8 raises the possibility that this tryptase regulates the steady state levels of neutrophil-sp ecific chemokines in vivo during mast cell-mediated inflammatory event s.