Docosahexaenoic Acid-Mediated Cytotoxicity in Immortalized Cells

Abstract

Docosahexaenoic acid (22:6n3, DHA) is an n-3 polyunsaturated fatty acid (PUFA) that is known to induce context-dependent cell survival, as well as apoptosis, but the exact cellular and molecular mechanism(s) remain unknown. DHA is known to act as a natural ligand for the peroxisome proliferator-activated receptors (PPARs) family of nuclear receptor, which may in turn influence cellular death. This thesis focused on the PPAR-mediated mechanistic induction of cell death, involving the accumulation of ceramide in an immortalized cell line treated with DHA. We utilized DHA treatment, with and without a specific inhibitor of PPARδ, GSK 3787. Our results validated PPARδ as a DHA target, which subsequently leads to the production of de novo ceramide, and apoptotic cell death. Various pathways leading to cell death were significantly attenuated with the simultaneous treatment of cells with DHA and GSK 3787, providing evidence that activation of PPARδ is vital to this process. Furthermore, we demonstrate that epoxydocosapentaenoates (EDPs) which are CYP oxidase metabolites of DHA induce a similar signaling pathway culminating in apoptotic cell death, suggesting that they are the active mediators. Our findings thus provide evidence for a novel pathway of DHA-mediated apoptotic cell death, and suggests that EDPs, and in particular 19, 20-EDP play a vital role in this process.