The role of cyclooxygenase-1 and cyclooxygenase-2 in lipopolysaccharide and interleukin-1 stimulated enterocyte prostanoid formation

LIPOPOLYSACCHARIDE is an inflammatory agent and interleukin-1 is a cytokine. Their pro-inflammatory effects may be mediated by prostanoids produced by inducible cyclooxygenase-2. The aim of this study was to determine the prostanoids produced by lipopolysaccharide and interleukin-l stimulated enterocytes through the cyclooxygenase-l and 2 pathways. Cultured enterocytes were stimulated with lipopolysaccharide or interleukin-1 beta with and without cyclooxygenase inhibitors. Low concentrations of indomethacin and valerylsalicylic acid (VSA) were evaluated as cyclooxygenase-l inhibitors and their effects compared with the effects of a specific cyclooxygenase-2 inhibitor, SC-58125. Prostaglandin E-2, 6-keto prostaglandin F-1 alpha prostaglandin D-2 and leukotriene B-4 levels were determined by radioimmunoassay. Immunoblot analysis using isoform-specific antibodies showed that the inducible cyclooxygenase enzyme (COX-2) was expressed by 4 h in LPS and IL-1 beta treated cells while the constitutive COX-1 remained unaltered in its expression. Interleukin-1 beta and lipopolysaccharide stimulated the formation of all prostanoids compared with untreated cells, but failed to stimulate leukotriene B-4. Indomethacin at 20 mu M concentration, and VSA inhibited lipopolysaccharide and interleukin 1 beta stimulated prostaglandin E-2, but not 6-keto prostaglandin F-1 alpha formation. SC-58125 inhibited lipopolysaccharide and interleukin-1 beta stimulated 6-keto prostaglandin F-1 alpha but not prostaglandin E-2 release. The specific cyclooxygenase-2 inhibitor also inhibited lipopolysaccharide produced prostaglandin D-2 but not interleukin-1 beta stimulated prostaglandin D-2 While SC-58125 inhibited basal 6-keto prostaglandin-F-1 alpha formation it significantly increased basal prostaglandin E-2 and prostaglandin D-2 formation. As SC-58125 inhibited lipopolysaccharide and interleukin-1 beta induced 6-keto prostaglandin F-1 alpha production but not prostaglandin E-2 production, it suggests that these agents stimulate prostacyclin production through a cyclooxygenase-2 mediated mechanism and prostaglandin E-2 production occurs through a cyclooxygenase-l mediated mechanism. Prostaglandin D, production appeared to be variably produced by cyclooxygenase-l or cyclooxygenase-2, depending on the stimulus.