Characterisation of P2Y(12) Receptor Responsiveness to Cysteinyl Leukotrienes

Leukotriene E(4) (LTE(4)), the most stable of the cysteinyl leukotrienes (cysLTs), binds poorly to classical type 1 and 2 cysLT receptors although in asthmatic individuals it may potently induce bronchial constriction, airway hyperresponsiveness and inflammatory cell influx to the lung. A recent study has suggested that the purinergic receptor P2Y(12) is required for LTE(4) mediated pulmonary inflammation in a mouse model of asthma and signals in response to cysLTs. The aim of the study was to characterise the responsiveness of human P2Y(12) to cysteinyl leukotrienes. Models of human CysLT(1), CysLT(2) and P2Y(12) overexpressed in HEK293, CHO cells and human platelets were used and responsiveness to different agonists was measured using intracellular calcium, cAMP and β-arrestin recruitment assays. CysLTs induced concentration dependent calcium mobilisation in cells overexpressing CysLT(1) and CysLT(2) but failed to induce any calcium response in cells expressing P2Y(12) or P2Y(12)+ Gα(16). In contrast, selective P2Y(12) agonists ADP and 2-MeS-ADP induced specific calcium flux in cells expressing P2Y(12)+ Gα(16). Similarly, specific response to 2-MeS-ADP, but not to cysLTs was also observed in cells expressing P2Y(12) when intracellular cAMP and β-arrestin signalling were analysed. Platelets were used as a model of human primary cells expressing P2Y(12) to analyse potential signalling and cell activation through P2Y(12) receptor or receptor heterodimers but no specific LTE(4) responses were observed. These results show that LTE(4) as well as other cysLTs do not activate intracellular signalling acting through P2Y(12) and suggest that another LTE(4) specific receptor has yet to be identified.