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 cyt okine. Their pro-inflammatory effects may be mediated by prostanoids p roduced by inducible cyclooxygenase-2. The aim of this study was to de termine the prostanoids produced by lipopolysaccharide and interleukin -l stimulated enterocytes through the cyclooxygenase-l and 2 pathways. Cultured enterocytes were stimulated with lipopolysaccharide or inter leukin-1 beta with and without cyclooxygenase inhibitors. Low concentr ations of indomethacin and valerylsalicylic acid (VSA) were evaluated as cyclooxygenase-l inhibitors and their effects compared with the eff ects 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 u sing isoform-specific antibodies showed that the inducible cyclooxygen ase enzyme (COX-2) was expressed by 4 h in LPS and IL-1 beta treated c ells while the constitutive COX-1 remained unaltered in its expression . Interleukin-1 beta and lipopolysaccharide stimulated the formation o f all prostanoids compared with untreated cells, but failed to stimula te leukotriene B-4. Indomethacin at 20 mu M concentration, and VSA inh ibited lipopolysaccharide and interleukin 1 beta stimulated prostaglan din E-2, but not 6-keto prostaglandin F-1 alpha formation. SC-58125 in hibited lipopolysaccharide and interleukin-1 beta stimulated 6-keto pr ostaglandin 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 form ation it significantly increased basal prostaglandin E-2 and prostagla ndin D-2 formation. As SC-58125 inhibited lipopolysaccharide and inter leukin-1 beta induced 6-keto prostaglandin F-1 alpha production but no t prostaglandin E-2 production, it suggests that these agents stimulat e prostacyclin production through a cyclooxygenase-2 mediated mechanis m and prostaglandin E-2 production occurs through a cyclooxygenase-l m ediated mechanism. Prostaglandin D, production appeared to be variably produced by cyclooxygenase-l or cyclooxygenase-2, depending on the st imulus.