Urinary trypsin inhibitor down-regulates hyaluronic acid fragment-induced prostanoid release in cultured human amnion cells by inhibiting cyclo-oxygenase-2 expression

We postulated that urinary trypsin inhibitor (UTI), a Kunitz-type protease inhibitor, may inhibit low molecular weight hyaluronic acid (HA) fragment-i nduced prostanoid release and de-novo expression of the inducible cyclo-oxy genase-2 (COX-2) isoform in human term amnion cells. Purified amnion cultur es were obtained from human fetal membranes and were exposed to a HA fragme nt (molecular weight 35 kDa) in the presence or absence of UTI (0-5.0 mu mo l/l). Amnion cells treated with the HA fragment (100 nmol/l) released signi ficantly more prostanoids (PGE(2) and PGF(2 alpha)) than controls PGE2: 2.1 +/- 0.13 pg/10(6) cells/24 h compared with 0.42 +/- 0.01, P < 0.05; PGF(2 alpha), 1.0 +/- 0.17 pg/106 cells/24 h compared with 0.13 rt 0.01, P < 0.05 ). UTI inhibited HA fragment-induced prostanoid release in a dose-dependent manner, with 50% inhibitory concentration values of 0.8 mu mol/l for PGE2 and 1.9 mu mol/l for PGF(2 alpha). Western blot analyses demonstrated that protein levels of COX-2 were substantially increased in amnion cells treate d with HA fragment. HA fragment-mediated COX-2 production was markedly dimi nished by pretreatment with UTI (1.0 mu mol/l). These results are the first to demonstrate that UTI is a potent inhibitor of HA fragment-induced arach idonic acid metabolism.