Exogenous fatty acids and niacin on acute prostaglandin D2 production in human myeloid cells

Niacin activates HCA₂ receptor that results in the release of PGD₂. However, little is known on PGD₂-producing cells and the role of fatty acids. Notably M-CSF macrophages exhibited a timely dependent PGD₂ production upon niacin challenge. Short pretreatment of M-CSF macrophages with autologous postprandial TRLs induced the down-regulation of HCA₂ gene and up-regulation of genes encoding COX1 and COX2 enzymes in a fatty acid-dependent manner. These effects were paralleled by a higher PGD₂ production with postprandial TRL-SFAs. The niacin-mediated transcriptional activity of all genes involved in PGD₂ biosynthesis was desensitized in a time-dependent manner by postprandial TRLs, leading to a decreased PGD₂ release. In vivo, the net excursions of PGD₂ in plasma followed similar fatty acid-dependent patterns as those found for PGD₂ release in vitro. The predominant fatty acid class in the diet acutely modulates PGD₂ biosynthetic pathway both in vitro and in vivo.