Peroxidation of 4-F4-neuroprostanes induces neurotoxicity in human neuroblastoma cells (SH-SY5Y)

Abstract

F4-neuroprostanes (F4-NeuroP), a non-enzymatically derived metabolite from the oxidation of docosahexaenoic acid (DHA), have shown to be elevated in some neurodegenerative diseases. Since its discovery, F4-NeuroP has been widely exploited as a sensitive biomarker for neuronal oxidative damages. While the onset of neurodegenerative diseases generally associates with the elevation of F4-NeuroP, it is speculated to play a role in neurodegenerative disease development. The hypothesis of its role in disease etiology and its exact molecular mechanism, however, still remains largely unclear, primarily due to the absence of commercially available chemical standards. Here, utilizing 4-series F4-NeuroP (4-F4-NeuroP) standard that we have in-house synthesized, the potential bioactivities of 4-F4-NeuroP was investigated. Determined by MTT assay, 4-F4-NeuroP (up to 100 μM) in SH-SY5Y human neuroblastoma cultured cells showed no signs of cellular toxicity. However, cell viability was significantly reduced when SH-SY5Y were co-treated with 4-F4-NeuroP and H2O2 as compared to control (H2O2), suggesting oxidized 4-F4-NeuroP, but not native 4-F4-NeuroP, is cytotoxic. On the contrary, qPCR results revealed that native 4-F4-NeuroP, not oxidized 4-F4-NeuroP, treatment on SH-SY5Y cells activates the expression of antioxidant genes, such as hemeoxygenase-1 and catalase. Intriguingly, infusion of 4-F4-NeuroP in rats significantly induce the production of DHA and its hydroxylated product (HDoHE) in liver and brain tissues. Also, the fact that exogenous infused 4-F4-NeuroP were deposited in the rat brains might suggest that the elevation of 4-F4-NeuroP in different neurodegenerative diseases could also be attributed from other organs, and the mode of delivery is likely via the formation of a complex with serum albumin, a transportation mechanism similar to those peripheral free fatty acids, as suggested by isothermal calorimetry experiment. These results might propose that the endogenous neural 4-F4-NeuroP has a cellular protective mechanism by acting as an activator/mediator for the enzymatic antioxidant pathway and fatty acid synthesis pathways.