Studies on the effect of cysteinyl leukotrienes on human t cell differentiation and function
Antigen-specific Th2 cells are central to the pathogenesis of asthma and other allergic diseases. Th2 cells secrete the cytokines IL-4, IL-5 and IL-13, responsible for many of the features of allergic inflammation such as eosinophilia, IgE production and mucus hypersecretion. Cysteinyl leukotrienes (CysLTs) are known potent lipid mediators involved in mucus production, bronchoconstriction and leukocyte migration, and act via the receptors CysLTiR and CysLT2R. Recently, CysLTs have been implicated in Th2 responses in mouse models, although the exact mechanisms are unclear. Preliminary microarray studies on polarised human Thl and Th2 cells suggested a highly selective expression of CYSLTR1 by human Th2 cells. Subsequent RT-PCR analysis confirmed that Th2 cells selectively express CYSLTR1 mRNA at high levels. Calcium signalling experiments revealed that Th2 cells respond selectively to leukotrienes compared to Thl cells, with a rank order of potency similar to that reported for CysL R (LTD4>LTC4>LTE4). This profile of leukotrienes responsiveness was blocked using the known selective CysLTiR antagonists MK571, Montelukast and Zafirlukast. Additionally, the LTD4-induced signalling in Th2 cells is mediated via CysLTiR coupled to Gaq and Gaj proteins, which are blocked when using selective CysLTiR antagonists. Finally, LTD4 is a potent chemoattractant for Th2 cells, which migrate to LTD4 at low nanomolar concentrations in a dose-dependent manner. Migration of human Th2 cells towards LTD4 was inhibited by selective CysLTiR antagonist MK571. Interestingly, LTD4 had no significant effect on the proliferation or differentiation of Th2 cells, or on the expression of Th2-specific cytokines. Microarray studies on LTD4-treated Th2 cells identified key immediate early genes that were upregulated after 30 minutes of treatment, and that were differentially expressed compared to untreated cells. This is the first report that human T cell subsets express functional CysLTiR and important implications for our understanding of the anti-inflammatory effect mechanism of CysLTiR antagonists.
Networked Digital Library of Theses and Dissertations