The omega-3 fatty acid, eicosapentaenoic acid increases neural stem cell proliferation via endocannabinoid signalling and p38 mitogen-activated protein kinase (MAPK) activation

H Mandhair, R Fincham, S Dyall, F Molina-Holgado. University of Roehampton, London, UK

The endocannabinoid system plays a key role in regulating adult neurogenesis and potentially brain repair. The omega-3 fatty acid, eicosapentaenoic acid (EPA) has been shown to have beneficial effects in a variety of neurological conditions and stimulate neurogenesis. Emerging evidence suggests a complex crosstalk between the endocannabinoid system, omega-3 fatty acids and the immune system in the promotion of brain self-repair. This study investigated the effects of EPA on neural stem cell (NSC) fate and the role of endocannabinoid signalling pathways in these effects. Cultures of NSC were prepared from the cortex of day 16 (ED16) C57BL6 mice (WT) or interleukin-1β (IL-1β) deficient (KO) mice, All procedures meet the Animals (Scientific Procedures) Act 1986/ASPA Amendment Regulations 2012 as well as the EU Directive 86/609/EEC. EPA (10nM, t=24h) significantly increased NSC (WT) proliferation compared to untreated controls (25 % vs. control, P<0.05), as assessed by BrdU ELISA. The effects occurred in parallel with specific increases in the levels of phospho-p38 MAPK (23.8 % vs. control, P<0.05 vs. control). Prior administration with the selective CB1 (AM251) or CB2 (AM630) receptor antagonists (both 1 µM) inhibited the effects on proliferation (both P<0.05 vs. control and P<0.001 vs. EPA) and p38 MAPK levels (both P<0.05 vs. EPA) to a similar extent. In NSC from KO mice, the effects of EPA treatment were abolished, and proliferation was significantly decreased, along with significantly reduced phospho-p38 MAPK levels following treatment (both P<0.05 vs. control). Although analysis of the membrane phospholipids by gas chromatography showed 48 hr incubation with EPA significantly increased EPA levels in NSCs from both WT and KO mice (73.4% and 96.6%, respectively, both P<0.05 vs. control), it is currently unclear whether these effects are mediated via EPA or a metabolite of EPA. Overall, the results suggest that EPA enhances NSC proliferation via endocannabinoid signalling pathways, potentially mediated via p38 MAPK, providing crucial new insights into the regulatory effects of EPA in NSC fate and the pathways involved. Furthermore, the study provides the first evidence that IL-1β has an essential role in the effects of EPA in regulating NSC fate, suggesting an important interaction with the neuro-immune system, The results highlight the therapeutic potential of the interplay of EPA with endocannabinoid signalling in brain repair.

Supported by The Dowager Countess Eleanor Peel Trust (UK)