New induction of leukotriene A4 hydrolase by interleukin-4 and interleukin-13 in human polymorphonuclear leukocytes

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Abstract
Interleukin (IL)-4, IL-10, and IL-13, Th2 cell–derived cytokines, play major roles in the pathophysiology of allergic diseases. These cytokines up-regulate or down-regulate the production of arachidonic acid metabolites. In this study, we have investigated the effect of IL-4, IL-10, IL-13, and other cytokines on A23187-stimulated synthesis of leukotriene (LT) B4 in human polymorphonuclear leukocytes (PMNs). Production of LTB4 was measured by specific radioimmunoassay and high performance liquid chromatography. Messenger RNA (mRNA) expression of cytosolic phospholipase A2 (cPLA2), 5-lipoxygenase (5-LO), and LTA4 hydrolase, which were involved in the synthesis of LTB4, was determined by reverse transcription–polymerase chain reaction and Northern blot analysis. Protein synthesis of their enzymes was determined by Western blot analysis. IL-4 and IL-13 enhanced A23187-stimulated LTB4 synthesis and increased mRNA expression and protein synthesis of LTA4hydrolase, but not those of cPLA2 or 5-LO. These results indicate that IL-4 and IL-13 transcriptionally or post-transcriptionally up-regulate the synthesis of LTB4, a potent chemotactic factor to PMNs, at the enzyme level of LTA4 hydrolase, and this up-regulation mechanism may participate in the development of allergic inflammation.

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