Impact of omega-6 polyunsaturated fatty acid supplementation and γ-aminobutyric acid on astrogliogenesis through the endocannabinoid system.

ABSTRACT

Neural stem cells express cannabinoid CB1 and CB2 receptors and the enzymes for the biosynthesis and metabolism of endocannabinoids (eCBs). Here we have studied the role of neural stem cell-derived eCBs as autonomous regulatory factors during differentiation. First, we examined the effect of an indirect eCB precursor linoleic acid (LA), a major dietary omega-6 fatty acid, on the eCB system in neural stem/progenitor cells (NSPCs) cultured in DMEM/F12 supplemented with N2 (N2/DF) as monolayer cells. LA upregulated eCB system-related genes and 2-arachidonoylglycerol (2-AG), but not anandamide (AEA), levels. Glial fibrillary acidic protein (GFAP) was significantly higher under LA-enriched conditions, and this effect was inhibited by the cannabinoid receptor type-1 (CB1) antagonist AM251. Second, the levels of AEA and 2-AG, as well as of the mRNA of eCB system-related genes, were measured in NSPCs after γ-aminobutyric acid (GABA) treatment. GABA upregulated AEA levels significantly in LA-enriched cultures and increased the mRNA expression of the 2-AG-degrading enzyme monoacylglycerol lipase. These effects of GABA were reproduced under culture conditions using neurobasal media supplemented with B27, which is commonly used for neurosphere culture. GABA stimulated astroglial differentiation in this medium as indicated by increased GFAP levels. This effect was abolished by AM251, suggesting the involvement of AEA and CB1 in GABA-induced astrogliogenesis. This study highlights the importance of eCB biosynthesis and CB1 signalling in the autonomous regulation of NSPCs and the influence of the eCB system on astrogliogenesis induced by nutritional factors or neurotransmitters, such as LA and GABA.