Thromboxane A2 up-regulates neutrophil elastase release in Syrian hamsters with trinitrobenzene sulfonic acid-induced...

Neutrophil elastase (NE) is a factor that aggravates colitis. We investigated the influence of thromboxane A2 (TXA2) and leukotriene B4 (LTB4) on NE release in Syrian hamsters with trinitrobenzene sulfonic acid-induced colitis. Colonic specimens with colitis were incubated with U-46619 (a TXA2 analogue) or LTB4 in vitro and NE release was examined. As a result, U-46619 increased NE release, while LTB4 had no effect. The NE release induced by U-46619 was inhibited by a TP-receptor antagonist. To demonstrate that TXA2 caused NE release in vivo as well, while LTB4 did not, colitis animals were treated with nordihydroguaiaretic acid (NDGA), a dual inhibitor of cyclooxygenase/lipoxygenase; and colonic luminal TXB(A)2 and LTB4 levels and NE activity were determined. The TXB(A)2 level was significantly correlated with NE activity, while no correlation was found between LTB4 and NE activity. An inhibitory effect of NDGA on the ulcer area was also observed, and NE activity was significantly correlated with the ulcer area. The suppression of TXA2 production by NDGA may result in the inhibition of NE release so that colonic tissue damage becomes less severe. Regulation of NE release is a new biological action of TXA2 that has not been reported before.