Regulation of eicosanoid production in rabbit colon by interleukin-1

Abstract

Prostaglandins and thromboxanes are increased in human and experimental colitis, but the factors that regulate this enhanced production are unclear. The present studies evaluate the effects of the monokines, interleukin-1 alpha and beta on eicosanoid production in rabbit colon. In tissue incubations the peak dose response of eicosanoid release to human recombinant interleukin-1 is 50 ng/ml. Interleukin-1 alpha increases prostaglandin E2 (PGE2) by 4.5 +/- 1.9 ng/g tissue, 6-keto PGF1 alpha by 6.2 +/- 2.7 ng/g, and thromboxane B2 by 2.1 +/- 0.3 ng/g compared to placebo. In isolated rabbit colons perfused with Krebs' solution, 10-h infusion of interleukin-1 alpha (50 ng/ml) progressively increases production of PGE2, 6-keto PGF1 alpha, and thromboxane B2. Bolus injections of bradykinin increase production of PGE2, but not 6-keto PGF1 alpha and thromboxane B2, and these responses are markedly augmented by interleukin-1 alpha: at 10 h bradykinin-stimulated PGE2 production is 518 +/- 104 vs. 95 +/- 18 ng/5 min (p less than 0.005), 6-keto PGF1 alpha is 172 +/- 88 vs. 8 +/- 2 ng/5 min (p less than 0.02), and thromboxane B2 is 60 +/- 14 vs. 13 +/- 4 ng/5 min (p less than 0.02) for interleukin-treated colons vs. placebo-treated colons, respectively. The response is greater with interleukin-1 alpha than interleukin-1 beta. This study demonstrates that interleukin-1 stimulates prostaglandin and thromboxane production in normal colon tissue. These data are consistent with the concept that interleukin-1 production by inflammatory cells may augment prostaglandin and thromboxane production in colitis.