Human umbilical vein endothelial cells generate leukotriene C-4 via microsomal glutathione S-transferase type 2 and express the CysLT(1) receptor

Certain immunocompetent myeloid cells, such as eosinophils, basophils and m ast cells, have a large capacity to synthesize the potent proinflammatory a nd spasmogenic mediator leukotriene (LT) C-4 via a specific microsomal glut athione S-transferase (MGST) termed LTC4 synthase (LTC4S). Here, we report that MGST2, a distant homologue of LTC4S, is abundantly expressed in Human umbilical vein endothelial cells (HUVEC) and converts LTA(4) into a single product, LTC4. Thus, using Northern blot, RT-PCR, Western blot, and enzyme activity assays, we show that MGST2 is the main, if not the only, enzyme th at converts LTA(4) into LTC4 in membrane preparations of HUVEC. In fact, we failed to detect any expression of LTC4S, MGST1 or MGST3 in these cells, i ndicating that MGST2 is a critical enzyme for transcellular LTC4 biosynthes is in the vascular wall. Unlike LTC4S, MGST2 prefers the naturally occurrin g free acid of LTA(4) over the methyl ester as substrate and is also suscep tible to product inhibition with an IC50 of about 1 mum for LTC4. Moreover, HUVEC were found to express the CysLT(1) receptor in line with a paracrine and autocrine role for cysteinyl-leukotrienes in endothelial cell function .