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

Abstract

We postulated that urinary trypsin inhibitor (UTI), a Kunitz-type protease inhibitor, may inhibit low molecular weight hyaluronic acid (HA) fragment-induced prostanoid release and de-novo expression of the inducible cyclo-oxygenase-2 (COX-2) isoform in human term amnion cells. Purified amnion cultures were obtained from human fetal membranes and were exposed to a HA fragment (molecular weight 35 kDa) in the presence or absence of UTI (0-5.0 micromol/l). Amnion cells treated with the HA fragment (100 nmol/l) released significantly more prostanoids (PGE2 and PGF2alpha) than controls (PGE2: 2.1 +/- 0.13 pg/10(6) cells/24 h compared with 0.42 +/- 0.01, P < 0.05; PGF2alpha: 1.0 +/- 0.17 pg/10(6) cells/24 h compared with 0.13 +/- 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 micromol/l for PGE2 and 1.9 micromol/l for PGF2alpha. Western blot analyses demonstrated that protein levels of COX-2 were substantially increased in amnion cells treated with HA fragment. HA fragment-mediated COX-2 production was markedly diminished by pretreatment with UTI (1.0 micromol/l). These results are the first to demonstrate that UTI is a potent inhibitor of HA fragment-induced arachidonic acid metabolism.