Linoleic acid‐derived metabolites constitute the majority of oxylipins in the rat pup brain and stimulate axonal growth in primary rat cortical neuron‐glia co‐cultures in a sex‐dependent manner

Author(s): Hennebelle, Marie; Morgan, Rhianna K; Sethi, Sunjay; Zhang, Zhichao; Chen, Hao; Grodzki, Ana Cristina; Lein, Pamela J; Taha, Ameer Y | Abstract: In adult rats, omega-6 linoleic acid (LA, 18:2n-6) serves as a precursor to oxidized LA metabolites (OXLAMs) known to regulate multiple signaling processes in the brain. However, little is known regarding the levels or role(s) of LA and its metabolites during brain development. To address this gap, fatty acids within various brain lipid pools, and their oxidized metabolites (oxylipins) were quantified in brains from one-day old male and female pups using gas chromatography and liquid chromatography coupled to tandem mass spectrometry, respectively. Primary neuron-glia co-cultures derived from postnatal day 0-1 male and female rat neocortex were exposed to vehicle (0.1% ethanol), LA, the OXLAM 13-hydroxyoctadecadienoic acid (13-HODE), or prostaglandin E2 (PGE2) at 10-1,000 nM for 48 h to test their effects on neuronal morphology. In both male and female pups, LA accounted for less than 3% of fatty acids detected in brain phospholipids, triacylglycerides, cholesteryl esters and free fatty acids, whereas OXLAMs constituted 46 to 52% of measured oxylipins (versus ~5% reported in adult rat brain). Of these, 13-HODE was the most abundant, accounting for 31-32% of total OXLAMs. Brain fatty acid and OXLAM concentrations did not differ between sexes. LA and 13-HODE significantly increased axonal outgrowth. Separate analyses of cultures derived from male vs. female pups revealed that LA at 1, 50 and 1000nM, significantly increased axonal outgrowth in female but not male cortical neurons, whereas 13-HODE at 100 nM significantly increased axonal outgrowth in male but not female cortical neurons. PGE2 did not alter neuronal outgrowth in either sex. This study demonstrates that OXLAMs constitute the majority of oxylipins in the developing rat brain despite low relative abundance of their LA precursor, and highlights a novel role of LA and 13-HODE in differentially influencing neuronal morphogenesis in the developing male and female brain. This article is protected by copyright. All rights reserved.