Upregulation of COX-2 in cerebral microvascular endothelial cells by smooth muscle cell signals

Abstract

Cyclooxygenase (COX) isoform expression, intracellular localization, and function in endothelial cells from the newborn pig cerebral microvessels were investigated using COX-1- and COX-2-specific antibodies and the COX-2 inhibitor NS-398. Cerebral microvessels, microvascular endothelium, and cultured endothelial cells constitutively express both COX-1 and COX-2. NS-398 inhibits 70-90% of endothelial prostanoid production. Endothelial cells grown in noncontact coculture with smooth muscle cells for 24-48 h demonstrate a stable induction of COX-2 protein and an NS-398-sensitive increase in prostanoid synthesis. The induction of endothelial COX in mixed cell coculture is accompanied by intracellular redistribution of COX-2. In cocultured endothelial cells, COX-2 is observed in the nucleus, nuclear envelope, and cytoplasm, compared with the mainly intranuclear localization of COX-2 in cells cultured separately. No changes were observed in COX-1 protein, localized in endothelial cell cytoplasm and the nuclear envelope. These results indicate that smooth muscle cells may modify endothelial function by upregulating COX-2, which is a major functional COX isoform in cerebral microvascular endothelial cells.