IgE-activated human lung mast cells preferentially release Prostaglandin D2, Tromboxane A2 and Cysteinyl-Leukotrienes

The capacity of human lung mast cells (HLMC) to biosynthesise lipid mediators other than prostaglandin D2 (PGD2) and the cysteinyl leukotrienes (CysLT) is not established. We therefore profiled lipid mediator metabolites in IgE-activated HLMCs. An LC-MS/MS platform including 107 metabolites of main endogenous polyunsaturated fatty acids (PUFAs) was applied to supernatants of HLMC and for comparison on material from in vitro developed cord blood mast cells (CBMC). Involved pathways were defined by the use of specific pharmacologic inhibitors and transcriptomic analysis of the expression of relevant enzymes. IgE-activation of HLMC profoundly increased the release of leukotriene (LT) C4 (> 500 times), PGD2 (> 200 times), and thromboxane (TX) B2 (> 100 times). In contrast, only minimal production of PGE2, LTB4 or lipoxin (LX) A4 was detected. The majority of the quantified compounds (n=50) were metabolites of arachidonic acid, whereas levels of metabolites from other PUFAs were low. Despite the COX-2 transcript being the most abundant species, all prostanoids, as well as LXA4 and 15-HETE, were solely biosynthesised in reactions catalyzed by COX-1. There was no apparent shunting between the main enzymatic pathways when COX-1 or 5-LOX were inhibited. Similar results were obtained in the CBMC model. There is a high degree of specialisation in HLMC with a strong and specific increase in CysLTs and PGD2 but also the bronchconstrictor TXA2 following IgE-depCendent activation. The primary lipid mediators to target for treatment of allergic asthma are PGD2, TXA2 and CysLTs.