A functional study on CysLT(1) receptors in human eosinophils

Abstract

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 flow-cytometric analysis for CysLT(1). Binding assays were performed with [(3)H]LTD(4). Purified eosinophils loaded with Fura-2 acetoxymethyl ester were stimulated with CysLTs, and Ca(2+) influx was measured. Eosinophil migration in response to CysLTs was measured using a 96-well multiwell Boyden chamber. Eosinophils were treated with LTD(4) at 10(-6) M for 60 min followed by incubation for 4 h at 37 degrees C 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 [(3)H]LTD(4)-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 Ca(2+) 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 LTD(4), LTC(4) and LTE(4). LTD(4) stimulated eosinophils to migrate at 10(-6) M via CysLT(1). LTE(4) also induced significant eosinophil migration at 10(-6) M. LTD(4) 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.