Modulation of Arachidonic Acid Metabolism in Niemann-Pick Disease Type C Cells

Hiroyuki      Nakamura

Abstract

Niemann-Pick disease type C (NPC) is a neurodegenerative lipid storage disorder caused by mutations in NPC1 or NPC2 genes. Loss of function of either protein results in the endosomal accumulation of cholesterol and other lipids. The mechanism of neuro-toxicity induced by the lipid storage has not been well elucidated. Here, we report that NPC1-deficient Chinese hamster ovary cells exhibit increased release of arachidonic acid (AA) and synthesis of prostaglandin E2 compared with wild-type cells. The enhanced release of AA was inhibited by both treatment with the selective inhibitor of cytosolic phospholipase A2α (cPLA2α) and cultivation in lipoprotein-deficient medium. There was no difference in the expression of both cyclooxygenase-1 and -2 between NPC cells and wild-type cells. U18666A, a cholesterol transport-inhibiting agent commonly used to mimic NPC, also increased the release of AA in L929 mouse fibrosarcoma cells. Furthermore, U18666A induced formation of reactive oxygen species, and induced cell death and cell cycle delay/arrest in L929 cells. Interestingly, these responses induced by U18666A were much weaker in cPLA2α knockdown L929 cells. These results suggest that cPLA2α-AA pathway plays important roles in the cytotoxicity and the reactive oxygen species formation in NPC cells.

Keywords: arachidonic acid, cytosolic phospholipase A2α, cytotoxicity, Niemann-Pick disease type C, reactive oxygen species, cell cycle, cholesterol