A functional study on CysLT1 receptors in human eosinophils

Background. The cysteinyl leukotrienes (CysLTs) mediate their biological actions through two receptors: CysLT(1) receptor and CysLT(2) receptor. Objective: This study was undertaken to examine the direct effects of CysLTs on eosinophils, such as chemotaxis and degranulation, focusing on CysLT(1). Methods: Eosinophils were isolated from venous blood from normal volunteers who had no history of allergy (purity >99%). They were subjected to reverse transcription-PCR analysis and flowcytometric analysis for CysLT(1). Binding assays were performed with [H-3]LTD4. Purified eosinophils loaded with Fura-2 acetoxymethyl ester were stimulated with CysLTs, and Ca2+ influx was measured. Eosinophil migration in response to CysLTs was measured using a 96-well multi-well Boyden chamber. Eosinophils were treated with LTD4 at 10(-6) M for 60 min followed by incubation for 4 h at 37degreesC in the presence or absence of IL-5 and eosinophil-derived neurotoxin (EDN) release was evaluated. Results: The expression of the mRNA and protein of CysLT(1) on eosinophils and [H-3]LTD4-specific binding to eosinophils were observed. Neither Th1 cytokine (IFN-gamma) nor Th2 cytokines (IL-4 or IL-5) affected CysLT(1) expression in eosinophils. CysLTs induced an increase in intracellular free Ca2+ in eosinophils via CysLT(1), as suggested by the efficient inhibition by a CysLT(1) antagonist, pranlukast, in addition to the rank order of potency being LTD4, LTC4 and LTE4. LTD4 stimulated eosinophils to migrate at 10(-6) M via CysLT(1). LTE4 also induced significant eosinophil migration at 10(-6) M. LTD4 enhanced EDN release induced by IL-5 via CysLT(1). Conclusion: CysLTs induce migration and enhance degranulation in eosinophils via CysLT(1). Accordingly, interaction of CysLTs and CysLT(1) on eosinophils has the potential to play a prominent role in the pathophysiology of asthma. Copyright (C) 2002 S. Karger AG, Basel.