Are proteases used as anti-inflammatory agents in reality accelerating theinflammatory process?

A possible anti-inflammatory effect of intraduodenally administered trypsin was investigated using the paw oedema and pleurisy models of carrageenan-i nduced inflammation in rats. No anti-inflammatory effect was detected by pl ethysmography or on the basis of pleural leukocyte migration in treated ani mals compared to a sham group. The groups were implanted with an intraduode nal catheter after treatment with metopyrone, an inhibitor of endogenous co rticosteroid synthesis. Since surgical stress induces an anti-inflammatory effect of its own; the sham group was an important control. Metopyrone anta gonized surgical stress, and trypsin inhibited oedema by about 16% four hou rs after carrageenan administration, a nonsignificant reduction. Evans blue dye protein leakage into the peritoneal cavity as a measure of vascular pe rmeability demonstrated a pro-inflammatory effect of trypsin. The present r esults lead us to propose that trypsin may be acting not as anti-inflammato ry agent but by accelerating the inflammatory process, thereby reducing the duration of the process. (C) 2000 Harcourt Publishers Ltd.