Altered eicosanoid biosynthesis in selenium-deficient endothelial cells

Selenium (Se) is an integral part of the Se-dependent glutathione peroxidase (Se-GSH-Px) catalytic domain. By modulating the cellular levels of fatty acid hydroperoxides, Se-GSH-Px can influence key enzymes of arachidonic acid cascade, in this case cyclooxygenase (COX) and lipoxygenase (LOX). To investigate this phenomenon, the effects of cellular Se status on the enzymatic oxidation of arachidonic acid were investigated in bovine mammary endothelial cells (BMEC), which were cultured in either Se-deficient (−Se) or Se-adequate (+Se) media. When stimulated with calcium ionophore A23187, BMEC produced eicosanoids of both COX and LOX pathways. Compared with the Se-adequate cells, the production of prostaglandin I2 (PGI2), prostaglandin F2 (PGF2α), and prostaglandin E2 (PGE2) was significantly decreased in Se-deficient cells, whereas the production of thromboxane A2 (TXA2) was markedly increased in the −Se BMEC cultures. Although the enzymatic oxidation of arachidonic acid by the LOX pathway was found to be relatively less than by the COX pathway, the BMEC cultured in −Se media produced significantly more 15-hydroperoxyeicosatetraenoic acid (15-HPETE) than the +Se cells produced. Based on these results, we postulate that cellular Se status plays an important regulatory role in the enzymatic oxidation of arachidonic acid by the COX and LOX pathways. The altered eicosanoid biosynthesis, especially the overproduction of 15-HPETE, in −Se BMEC may be one of the underlying biochemical phenomena responsible for vascular dysfunction during Se deficiency.