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IL-13 and IL-4 Up-Regulate Cysteinyl Leukotriene 1 Receptor Expression in Human Monocytes and Macrophages1

The cysteinyl (Cys) leukotrienes (LT)C4, LTD4, and LTE4, are lipid mediators that have been implicated in the pathogenesis of asthma. The human LTD4 receptor (CysLT1R) was recently cloned and characterized. The present work was undertaken to study the potential modulation of CysLT1R expression by the Th2 cytokines IL-13 and IL-4. In this study, we report that IL-13 up-regulates CysLT1R mRNA levels, with consequently enhanced CysLT1R protein expression and function in human monocytes and monocyte-derived macrophages. CysLT1R mRNA expression was augmented 2- to 5-fold following treatment with IL-13 and was due to enhanced transcriptional activity. The effect was observed after 4 h, was maximal by 8 h, and maintained at 24 h. IL-4, but not IFN-γ, induced a similar pattern of CysLT1R up-regulation. Monocytes pretreated with IL-13 or IL-4 for 24 h showed enhanced CysLT1R protein expression, as assessed by flow cytometry using a polyclonal anti-CysLT1R Ab. They also showed enhanced responsiveness to LTD4, but not to LTB4, in terms of Ca2+ mobilization, as well as augmented chemotactic activity. Our findings suggest a possible mechanism by which IL-13 and IL-4 can modulate CysLT1R expression on monocytes and macrophages, and consequently their responsiveness to LTD4, and thus contribute to the pathogenesis of asthma and allergic diseases.